What Is The Non-Towered Traffic Pattern "Size"?

[dmccormack]

I'm of the group that will find somewhere out front to put her down. I have a dozen places located all around the airport where I plan on putting my plane if the engine ever goes out on me while I'm taking off or landing, and only one of them is the runway. I'm still wondering why you want to stay within gliding distance of the runway at all times.

Good, and I'm in that club too, unless I know the airplane -- then I have an altitude AGL I will use as the "No turning back" line.

Anything below that, it's straight (or as straight) as possible.

As far as the pattern size...

As Bruce quoted from the AFH, "1/2 mile from runway centerline" is the guideline (not regulatory). The "within gliding distance" guidance IMHO is an artifact of earlier times with less reliable engines.

That said, I'm not sure why you would want to be further out that "gliding distance," as there seems to be no clear advantage to a big pattern.

 

[Maxmosbey]

Good, and I'm in that club too, unless I know the airplane -- then I have an altitude AGL I will use as the "No turning back" line.

Anything below that, it's straight (or as straight) as possible.

As far as the pattern size...

As Bruce quoted from the AFH, "1/2 mile from runway centerline" is the guideline (not regulatory). The "within gliding distance" guidance IMHO is an artifact of earlier times with less reliable engines.

That said, I'm not sure why you would want to be further out that "gliding distance," as there seems to be no clear advantage to a big pattern.

When you say gliding distance, do you mean losing the engine and being in a position to put it into a glide, get out off one end of the runway or the other, lining it up and bringing it in for a dead stick landing somewhere on the runway itself, of just getting it somewhere on the airport? This is where I'm having trouble with the concept of "gliding distance." That is a lot of gliding. I am in agreement with you on wide patterns. If left to my own, I'll fly it tight, but only because I like to make a short base.

 

[dmccormack]

When you say gliding distance, do you mean losing the engine and being in a position to put it into a glide, get out off one end of the runway or the other, lining it up and bringing it in for a dead stick landing somewhere on the runway itself, of just getting it somewhere on the airport? This is where I'm having trouble with the concept of "gliding distance." That is a lot of gliding. I am in agreement with you on wide patterns. If left to my own, I'll fly it tight, but only because I like to make a short base.

I try to keep the scenario simple -- you've lost your one and only engine.

Thus the next task is to land where you will the least harm to your passengers, yourself, people on the ground, and the airplane (in that order).

Actually, many students and even experienced pilots try to land on the numbers after an engine out.

Forget that! You're in a real emergency-- especially along the east coast where airports are now surrounded by housing and other developments.

Just get it down -- if the engine quits midfield downwind, do whatever it takes -- even if that means a touch down halfway along a 4000' runway in a 172...
...or landing any available taxiway because a twin is "Position and Hold" on the active...
...or if you took off on 18, landing on intersecting runway 12...

It's one of the reasons I (at the very least) demonstrate S turns to PP and Comm students -- sometimes you're too high to slip -- now what?

The Power Off, 180 accuracy landing is a PTS Commercial maneuver.

But it sure as heck isn't required when the engine really dies.

 

[bbchien]

The Power Off, 180 accuracy landing is a PTS Commercial maneuver.

But I think every PVT ASEL should be capable of this.

But it sure as heck isn't required when the engine really dies.

I'm more afraid that some bozo will insist on landing first when it does quit.

 

[dmccormack]

But I think every PVT ASEL should be capable of this.

Absolutely!

 

[Easterner]

Does this work as a quantitative approach to the OP's question? The geometry of the pattern, combined with the turn radius equation, yields the answer (for no-wind conditions and a given bank angle).

If you want to turn max 20 degrees AoB, and spend 0.2nm in S&L flight on base, here are the numbers (in the following order):
airspeed...distance flown from abeam the numbers...time from abeam the numbers....length of s&l flight on final...distance from centerline:

70kts...2.0nm...1.7min...0.6nm...0.6nm
90kts...2.9nm...2.5min...0.9nm...0.9nm
110kts...4.1nm...3.5min...1.2nm...1.2nm

The radius of the turns from downwind to base, and from base to final, summed with the distance you'd like to spend in S&L base, that gives you the distance from centerline, which is the same as the distance flown on final, due to the geometry of the pattern. Finally, the time spent in flight of these standard pattern distances, less the very slight loss of energy from shallow-bank turns, gives you the required vertical velocity.

 

[dmccormack]

Does this work as a quantitative approach to the OP's question? The geometry of the pattern, combined with the turn radius equation, yields the answer (for no-wind conditions and a given bank angle).

If you want to turn max 20 degrees AoB, and spend 0.2nm in S&L flight on base, here are the numbers (in the following order):
airspeed...distance flown from abeam the numbers...time from abeam the numbers....length of s&l flight on final...distance from centerline:

70kts...2.0nm...1.7min...0.6nm...0.6nm
90kts...2.9nm...2.5min...0.9nm...0.9nm
110kts...4.1nm...3.5min...1.2nm...1.2nm

The radius of the turns from downwind to base, and from base to final, summed with the distance you'd like to spend in S&L base, that gives you the distance from centerline, which is the same as the distance flown on final, due to the geometry of the pattern. Finally, the time spent in flight of these standard pattern distances, less the very slight loss of energy from shallow-bank turns, gives you the required vertical velocity.

Is this Sean Tucker?

You have to be to fly this precisely...

 

[Easterner]

I couldn't fly it this precisely in my dreams!

But, the exercise was kind of useful: the spreadsheet results helped reveal why the AFH recommends the distances it does.

What was interesting to me about this was that even if you fly the whole pattern at 110 kts, which is pretty darned fast compared to what we bug-smashers are used to, it does not have to be a very wide or long pattern.

Could somebody tell me something else, on this subject? Why is it you extend flaps in a 172 on each of the three legs? It seems much safer to extend 20 degrees in the downwind, and just leave it there; fly the same airspeed all the way down, and land like that (assuming no short field, of course). Why stick your head down three separate times (even briefly), and have the extra control forces changes, and worst of all, risk a split flap condition at 400 ft AGL?

I am sure there is a good reason, something better than "we've always done it that way."

 

[poadeleted20]

Could somebody tell me something else, on this subject? Why is it you extend flaps in a 172 on each of the three legs? It seems much safer to extend 20 degrees in the downwind, and just leave it there; fly the same airspeed all the way down, and land like that (assuming no short field, of course). Why stick your head down three separate times (even briefly), and have the extra control forces changes, and worst of all, risk a split flap condition at 400 ft AGL?

I'll start at the end -- there's no need to go "head down" when extending flaps. You should be able to reach the switch and extend the desired amount of flaps without looking.

As for the rest, there are several reasons. One is that it keeps noise down for the neighbors -- the more flaps you use, the more power you need to fly the same pattern. In addition, most folks don't like to extend full flaps until committing to land because full flaps makes a go-around a lot tougher, or at high DA's, even impossible. In most cases, you aren't assured of landing until you get on final, since a lot of things can happen between downwind and that point to force a go-around, but not many past that point.

A final point is that in the 172, you can extend 10 flaps at near cruise speeds (110 KIAS, IIRC) to help you slow down, but can't extend more until you get below (IIRC) 85 knots IAS, which you reach easily after extending 10 flaps to get slowed.

 

[dmccormack]

Could somebody tell me something else, on this subject? Why is it you extend flaps in a 172 on each of the three legs? It seems much safer to extend 20 degrees in the downwind, and just leave it there; fly the same airspeed all the way down, and land like that (assuming no short field, of course). Why stick your head down three separate times (even briefly), and have the extra control forces changes, and worst of all, risk a split flap condition at 400 ft AGL?

I am sure there is a good reason, something better than "we've always done it that way."

There is no requirement -- FAA, POH, or otherwise -- to extend flaps incrementally.

There are several reasons this technique is taught. Some include:

• reduce the amount of pitch change required when decelerating and adding flaps (to whatever the maximum setting may be)
• allow a steady reduction in airspeed from downwind to final
• allow the pilot to make adjustments to track base don winds (which often change in intensity and direction from pattern altitude to touchdown).

There's no fault in dropping full flaps when abeam the aiming point, just be sure you can make the runway with all that drag.

But all pilots should be able to vary techniques to adapt to the particular situation. Pilots who fly left patterns with particular flaps settings at particular points in the pattern will have a tough time on a straight in, right pattern, or an airport with a ridge or obstruction nearby.

Bottom line -- know the airplane and what a given combination of power, attitude, and configuration will do, and use as necessary.

 

[ScottM]

I'll start at the end -- there's no need to go "head down" when extending flaps. You should be able to reach the switch and extend the desired amount of flaps without looking.

As for the rest, there are several reasons. One is that it keeps noise down for the neighbors -- the more flaps you use, the more power you need to fly the same pattern. In addition, most folks don't like to extend full flaps until committing to land because full flaps makes a go-around a lot tougher, or at high DA's, even impossible. In most cases, you aren't assured of landing until you get on final, since a lot of things can happen between downwind and that point to force a go-around, but not many past that point.

A final point is that in the 172, you can extend 10 flaps at near cruise speeds (110 KIAS, IIRC) to help you slow down, but can't extend more until you get below (IIRC) 85 knots IAS, which you reach easily after extending 10 flaps to get slowed.

There is no requirement -- FAA, POH, or otherwise -- to extend flaps incrementally.

There are several reasons this technique is taught. Some include:

• reduce the amount of pitch change required when decelerating and adding flaps (to whatever the maximum setting may be)
• allow a steady reduction in airspeed from downwind to final
• allow the pilot to make adjustments to track base don winds (which often change in intensity and direction from pattern altitude to touchdown).

There's no fault in dropping full flaps when abeam the aiming point, just be sure you can make the runway with all that drag.

But all pilots should be able to vary techniques to adapt to the particular situation. Pilots who fly left patterns with particular flaps settings at particular points in the pattern will have a tough time on a straight in, right pattern, or an airport with a ridge or obstruction nearby.

Bottom line -- know the airplane and what a given combination of power, attitude, and configuration will do, and use as necessary.

Not much to add to these two posts but one more little reason that I can think of. During your approach you are slowing down. Just like in a car you make it comfortable by slowing decelerating. Pulling all the flaps at once will cause one to be thrown somewhat forward. So slowly apply flaps makes the process of transition from cruise speeds to landing speeds comfortable for the people in the airplane.

 

[dmccormack]

Not much to add to these two posts but one more little reason that I can think of. During your approach you are slowing down. Just like in a car you make it comfortable by slowing decelerating. Pulling all the flaps at once will cause one to be thrown somewhat forward. So slowly apply flaps makes the process of transition from cruise speeds to landing speeds comfortable for the people in the airplane.

What are you flying, Scott?




For larger, faster airplanes (twins, turbines, etc) the gradual application makes plenty of sense for the reason you described. Lots of Flight Training is geared towards future Transport Pilots, so that may explain this technique's ubiquity.

But for the typical GA SEL, a reasonable downwind speed can eliminate this sensation.

In a 150 knot retract, for instance, I use no more than 100 KIAS on downwind. Final Approach speed is 80 (73 ((light)-78 ((heavy)) for short field), so the speed transition is rather slight.

 

[ScottM]

But for the typical GA SEL, a reasonable downwind speed can eliminate this sensation.

Even on small planes going form 0 to 40 degrees of flaps will give you that sensations. not to mention it will throw the nose up causing the pilot to have to push forward with greater effort than normal.

But I do agree on most light GA planes power control helps take care of a lot of mitigating the problem.

 

[dmccormack]

Even on small planes going form 0 to 40 degrees of flaps will give you that sensations. not to mention it will throw the nose up causing the pilot to have to push forward with greater effort than normal.

True on Cessnas with 40 degree flaps, but you should be able to anticipate the pitch up and compensate with forward pressure on the yoke, mais non?

 

[poadeleted20]

True on Cessnas with 40 degree flaps, but you should be able to anticipate the pitch up and compensate with forward pressure on the yoke, mais non?

One of my goals is to try to make it easy, and going from zero to 40 flaps in one gulp on downwind (or anywhere else, for that matter) doesn't accomplish that goal.

 

[dmccormack]

One of my goals is to try to make it easy, and going from zero to 40 flaps in one gulp on downwind (or anywhere else, for that matter) doesn't accomplish that goal.

Agreed -- 40 is a bit much -- but in Cessna airplanes I've flown with 40, I've saved 40 for short fld or calm or straight down the runway winds.

40 degrees makes a go-around a handful and seems to accentuate the wing lift from gusts of crosswinds.

That said -- if you slow the airplane down and trim to the target descent speed before adding flaps, there is usually little to no re-configuration or power change required to get a nice 500 FPM descent at the trim airspeed with 30 degrees of flaps all the way from turn to base to base to final.

It also helps tighten up those patterns.

Again -- I'm not advocating this as required, but rather a technique all pilots should be familiar with, and able to employ as needed.

 

[Easterner]

I think the practice of incremental flaps is taught out of inertia; it originated in the "paper aesthetics" of the approach. It just "made sense" to slow down a bit on each leg, and add flaps a bit on each leg, and so forth. But I think it is a bad practice.

In instrument flying, we set up a single configuration for a single purpose. Power + attitude + configuration = performance, and all that good stuff. Should not the same idea apply to the pattern? There is only one thing that needs to be down between downwind and the numbers: a descent with turns. Why do you need three configurations for that? You don't need three configurations in a descending procedure turn, and you had better not have them if you want to survive in the soup for very long.

You would need a really compelling operational reason to persuade me that configuration changes below 1000' AGL, either in the pattern or on an ILS, are a good idea. The FAA agrees, in principle: that is the driving force behind the stabilized approach concept.

Concerning 40 degrees of flaps all at once: other than in training or for proficiency, I no longer lower 40 degrees in any GA airplane for landing. There is almost never a good reason to do so in everyday flying, and there are many reasons not to.

A reasonable alternative pattern technique is just to reduce power and lower 25 degrees flaps, trim for x knots, and then fly a 3.5-degree glide path from abeam the numbers to the middle of the first third of the runway.

Using this technique, all of the pilot's attention is where it should be while in the pattern: on aircraft control, and on the scan.

If the engine quits anywhere but on short final, all you have to do is cut the corner of the next turn and you have the airfield (if not the runway) made. If it quits on final, at least you don't have barn doors hanging off the airplane.

 

[jesse]

Concerning 40 degrees of flaps all at once: other than in training or for proficiency, I no longer lower 40 degrees in any GA airplane for landing. There is almost never a good reason to do so in everyday flying, and there are many reasons not to.

Every airplane I've made makes a ****ty racecar on the runway. Therefore, I prefer to touch down on the runway as slow as I can. In every airplane I've flown, that means full flaps , and if that happens to be 40 degrees--that is what I use.

As far as when to do the flaps? There is no hard and fast rule. Do them when they will give you the result you need. Often in a Cherokee I dump full flaps abeam the numbers. In a Cessna 150, I might not add full flaps until short final, because the thing practically quits flying with all of them.

 

[flyingcheesehead]

Agreed -- 40 is a bit much -- but in Cessna airplanes I've flown with 40, I've saved 40 for short fld or calm or straight down the runway winds.

40 degrees makes a go-around a handful and seems to accentuate the wing lift from gusts of crosswinds.

That said -- if you slow the airplane down and trim to the target descent speed before adding flaps, there is usually little to no re-configuration or power change required to get a nice 500 FPM descent at the trim airspeed with 30 degrees of flaps all the way from turn to base to base to final.

Hmmm... I have some disagreements. Keep in mind that this is my perspective from the 182, which actually flies quite a bit different from the 172.

40 is not "a bit much." 40 is what the airplane was designed with, and there's not a darn thing wrong with using 40 on every single landing. Just a few hours ago, I had a landing on a runway that required a nearly 7,000 foot rollout to get to the correct taxiway. 40 flaps. A single new tire costs $380 - I'm gonna make 'em last as long as I can. Same with brakes.

From what I can tell, the people who do not use the full 40 degrees of flaps on the 182 are the people who really don't know how to fly it, and rather than practice and get better, they gave up and copped out and used 20.

As far as gusts - I don't buy it at all. In the 182, everything between 20 and 40 seems to add all drag and no lift. 20 flaps will kick your wing up. 40 won't - It'll just slow you down faster. As far as go-arounds - Well, that's why you put them up to 20 almost immediately after initiating the go-around.

I think the practice of incremental flaps is taught out of inertia; it originated in the "paper aesthetics" of the approach. It just "made sense" to slow down a bit on each leg, and add flaps a bit on each leg, and so forth. But I think it is a bad practice.

It works very well in the 182 - I don't need to look to know where the flap handle is or how far to move it. The 182 is heavy in pitch and has a significant pitch-up when adding flaps, which requires quite a muscular push on the yoke. I find that it's manageable when I add a notch of flaps, push and wait for the plane to slow down just a bit and catch up with the trim, stabilize, and repeat. Adding all 40 degrees at once would require a lot more force on the yoke than I'd be comfortable using.

In instrument flying, we set up a single configuration for a single purpose. Power + attitude + configuration = performance, and all that good stuff. Should not the same idea apply to the pattern? There is only one thing that needs to be down between downwind and the numbers: a descent with turns. Why do you need three configurations for that? You don't need three configurations in a descending procedure turn, and you had better not have them if you want to survive in the soup for very long.

Yeah, but we're not in the soup. Again, the single configuration would NOT work well for me at all. What works really well is to pull to 12" MP abeam the numbers, add 10 flaps, push, wait for the nose to come down a bit and the control forces to go away. On the downwind to base turn: Begin turn, tap flap switch to 20, push and/or let the pitch up forces help you in the turn, and after rolling out the airplane is once again stabilized. Base to final turn, same thing.

Concerning 40 degrees of flaps all at once: other than in training or for proficiency, I no longer lower 40 degrees in any GA airplane for landing. There is almost never a good reason to do so in everyday flying, and there are many reasons not to.

Hmmm...

For: Less wear and tear on tires and brakes, less energy to cause problems on the ground, less chance of a runway overrun or ground loop, steeper approach possible, etc...

Against: A pilot who's not comfortable in his plane might be more likely to screw up with multiple config changes, uhhh... I can't really think of another one offhand. Really, what are the "many" reasons not to?

If the engine quits anywhere but on short final, all you have to do is cut the corner of the next turn and you have the airfield (if not the runway) made. If it quits on final, at least you don't have barn doors hanging off the airplane.

If the engine quits, the barn doors are comin' up, ALL the way, and I'm gonna head for the nearest piece of grass on the airport if I can't make a runway.

 

[dmccormack]

40 is not "a bit much." 40 is what the airplane was designed with, and there's not a darn thing wrong with using 40 on every single landing. Just a few hours ago, I had a landing on a runway that required a nearly 7,000 foot rollout to get to the correct taxiway. 40 flaps. A single new tire costs $380 - I'm gonna make 'em last as long as I can. Same with brakes.

From what I can tell, the people who do not use the full 40 degrees of flaps on the 182 are the people who really don't know how to fly it, and rather than practice and get better, they gave up and copped out and used 20.

As far as gusts - I don't buy it at all. In the 182, everything between 20 and 40 seems to add all drag and no lift. 20 flaps will kick your wing up. 40 won't - It'll just slow you down faster. As far as go-arounds - Well, that's why you put them up to 20 almost immediately after initiating the go-around.

While I'm also an advocate of "Touch down with as little energy as possible," I don't think absolute rules apply to much in flying -- including landing.

First, while I use 40 in those airplanes that have 40 available the majority of the time, the fact is sometimes less than 40 works.

One reason is the lack of flap detent -- You press and hold on some of the older models. If you count you can get it right, but sometimes you don't and you have 35 or 29 or 37 degrees instead of 40 (Yeah, I'd like to pretend to be perfect, but I ain't).

Another is gusty conditions. 40 degrees of flaps will accentuate a wing lift due to gusts. I've had variable gusty days here in the hilly Western PA, WV region.

AFH Chapter 8:

To maintain good control, the approach in turbulent air with gusty crosswind may require the use of partial wing flaps. With less than full flaps, the airplane will be in a higher pitch attitude. Thus, it will require less of a pitch change to establish the landing attitude, and the touchdown will be at a higher airspeed to ensure more positive control.

Also, the difference between 30 and 40 in actual speed reduction is minimal (on the order of 1-2 knots). Some POH's have this information, but it can be verified by a stall series with each flaps setting and recording the AS at stall.

Finally, there are some approaches where you are asked to "keep the speed up." In those cases (such as twice yesterday at two different airports) I have 0 flaps until about 3 miles out, then slow the airplane up to landing speed with power and pitch, then add in flaps until the descent angle, airspeed, and touchdown point all come together (no matter the flap setting), land and keep it rolling to first taxiway.

So while I agree wholeheartedly with the goal of minimal energy on touchdown, and 40 degrees of flaps will help acheive that in those airplanes so equipped, I don't use all 40 every time.

 

[flyingcheesehead]

While I'm also an advocate of "Touch down with as little energy as possible," I don't think absolute rules apply to much in flying -- including landing.

Dan, I enjoy these discussions with you - So it's time for me to be a pest so I can figure out why I might want to change what I do.

First, while I use 40 in those airplanes that have 40 available the majority of the time, the fact is sometimes less than 40 works.

It certainly *works*, and many people who fly the plane less than I do (I fly it about the same number of hours in a year as the rest of the club combined) will say "it's easier to land with 20" so it clearly works. I just feel that it's not good technique most of the time.

One reason is the lack of flap detent -- You press and hold on some of the older models. If you count you can get it right, but sometimes you don't and you have 35 or 29 or 37 degrees instead of 40 (Yeah, I'd like to pretend to be perfect, but I ain't).

Ours has the detent... But wouldn't the push-and-hold variety be even MORE reason to use 40? The flaps do stop at 40 anyway, so if you use the full 40 you know you've got 40. It'd be the intermediate stops where you don't really know where they are.

Another is gusty conditions. 40 degrees of flaps will accentuate a wing lift due to gusts. I've had variable gusty days here in the hilly Western PA, WV region.

On the way to Gaston's, I landed at JEF with winds 20G29 60 degrees off the runway. There was no noticeable difference in the wing lifts between when I had 0 flaps and when I had 40, or anywhere in between. But, since we add half the gust factor when landing in these conditions, we have extra energy to dissipate and we want to dissipate it as quickly as possible to avoid getting blown back up in the air - That says full flaps to me. Maybe other planes are somehow more susceptible to lifting wings with full flaps vs. partial?

Also, the difference between 30 and 40 in actual speed reduction is minimal (on the order of 1-2 knots). Some POH's have this information, but it can be verified by a stall series with each flaps setting and recording the AS at stall.

I assume by "speed reduction" you mean "stall speed reduction"? If so, I agree - It's the drag I'm after. However, the detents on the 182 are 10, 20, and 40. The difference between 0 flaps and full is 5 knots.

Finally, there are some approaches where you are asked to "keep the speed up." In those cases (such as twice yesterday at two different airports) I have 0 flaps until about 3 miles out, then slow the airplane up to landing speed with power and pitch, then add in flaps until the descent angle, airspeed, and touchdown point all come together (no matter the flap setting), land and keep it rolling to first taxiway.

I practice those all the time - I can get to 325 AGL on the ILS glideslope at 140 knots and still put it on the numbers. However, to do so *requires* 40 flaps. A flat prop is a good brake, but I need the barn doors out to slow down that much that fast, so as soon as I'm at the white arc the flaps go all the way out.

So while I agree wholeheartedly with the goal of minimal energy on touchdown, and 40 degrees of flaps will help acheive that in those airplanes so equipped, I don't use all 40 every time.

So, you still don't have me convinced. I have yet to come up with a situation where I felt anything but 40 was a better option.

 

[dmccormack]

So, you still don't have me convinced. I have yet to come up with a situation where I felt anything but 40 was a better option.

You carefully ignored the quote from the AFH....

 

[dmccormack]

It certainly *works*, and many people who fly the plane less than I do (I fly it about the same number of hours in a year as the rest of the club combined) will say "it's easier to land with 20" so it clearly works. I just feel that it's not good technique most of the time.

116.2 hours in airplanes with 40 degrees of flaps in the last 4 months.

Does that count?

Ours has the detent... But wouldn't the push-and-hold variety be even MORE reason to use 40? The flaps do stop at 40 anyway, so if you use the full 40 you know you've got 40. It'd be the intermediate stops where you don't really know where they are.

No.

Though there is a limit switch, you run the risk of burning out the flap motor if you hold it past the full extension (especially if the limit switch died).

Now you need to go around and the flap motor is shot.

Now what?

On the way to Gaston's, I landed at JEF with winds 20G29 60 degrees off the runway. There was no noticeable difference in the wing lifts between when I had 0 flaps and when I had 40, or anywhere in between. But, since we add half the gust factor when landing in these conditions, we have extra energy to dissipate and we want to dissipate it as quickly as possible to avoid getting blown back up in the air - That says full flaps to me. Maybe other planes are somehow more susceptible to lifting wings with full flaps vs. partial?

The extension of flaps changes a number of aerodynamic factors. Each airplane model is different -- fowler? Slotted? Plain? Spit? Combination?

Center of Pressure differential? Elevator wash out?

You'd better have your airspeed right on the money if you extend full flaps in an A36 or you will float yourself right on down the runway.

I assume by "speed reduction" you mean "stall speed reduction"? If so, I agree - It's the drag I'm after. However, the detents on the 182 are 10, 20, and 40. The difference between 0 flaps and full is 5 knots.

Yes.. that's what I meant. The stall speed will usually vary only slightly after 20 degrees flaps. The first 20 degrees are mostly lift with relatively little drag. After 20 you increase drag with little gain in lift.

I practice those all the time - I can get to 325 AGL on the ILS glideslope at 140 knots and still put it on the numbers. However, to do so *requires* 40 flaps. A flat prop is a good brake, but I need the barn doors out to slow down that much that fast, so as soon as I'm at the white arc the flaps go all the way out.

Why would you put it on the numbers during an ILS?

The GS leads to the touchdown point -- not the numbers.

I haven't seen an ILS equipped runway yet that was so short I needed to do short field technique after coming in to minimums -- that's just plain risky, and unnecessary.

So, you still don't have me convinced. I have yet to come up with a situation where I felt anything but 40 was a better option.

That's more than fine -- but -- have you done all this flying and landing with CG loaded to aft limits?

You may convince yourself. Last thing I need to do is convince anybody of anything.

Keep in mind -- while I am also a proponent of minimal speed landings, I can't accept that 40 degrees is required every single time.

It's not.

You can fly 1.3 Vso in a Cessna with 20 degrees flaps. The only advantage to 40 degrees over 20 or 30 is a steeper descent angle for the same airspeed, period. You don't land any slower, you don't land any shorter (in fact to decrease ground roll you should move flaps up so the wheels can create friction).

 

[jesse]

You'd better have your airspeed right on the money if you extend full flaps in an A36 or you will float yourself right on down the runway.

I don't get what you're saying. You just got done saying all the extra flaps equals more drag. Now you're saying adding more flaps suddenly makes you float further.

I've found I can brick almost any airplane with throttle off, full nose up slip, full flaps when the needle hits the white arc, drop nose below horizon to prevent stall.

I haven't seen an ILS equipped runway yet that was so short I needed to do short field technique after coming in to minimums -- that's just plain risky, and unnecessary.

Kent is a friendly pilot that wants to help out GA. If ATC asks for you to keep it fast on final they generally are trying to get you out of the way for an airliner. Flying it in fast and landing it short off on the first taxiway makes room for that airliner behind you.

Kent also wants to be able to put a plane down safely in very little runway as he sometimes goes to airports with very little runway. In order to maximize every dollar spent--he often does this on longer runways.

You can fly 1.3 Vso in a Cessna with 20 degrees flaps. The only advantage to 40 degrees over 20 or 30 is a steeper descent angle for the same airspeed, period.

Nope. You also slow faster. It is easier to do the following with more flaps: Come in with some safe airspeed, pull the throttle to idle, dump that airspeed so that you can be stopped ASAP.

If there is an obstacle on a short runway I generally come in draggy as can be with power. Once I'm clear I pull to idle and throw it into a hard slip. The more flaps you have, the faster you'll slow down, and the faster you can come down. You *want* to come down fast on short runways.

If you're going to fly on short grass with trees from time to time, you really need to be good at it, else you end up a tree ordainment. Like Kent, I try to keep my short field landing skills perfect no matter if it's 1,200 feet or 10,000 feet.

You don't land any slower, you don't land any shorter (in fact to decrease ground roll you should move flaps up so the wheels can create friction).

You are very wrong. With more drag *you will* land shorter. You will slow faster in the air and you can slow to an airspeed that you can't easily climb at. On a real short field I keep a reasonable amount of airspeed to permit go arounds until short short final. At that point I dump all my excess airspeed and down I come.

I've landed on 1,200 grass with trees in a 172 before. You really want to use all the flaps you've got. The more drag the better because the moment you come over that obstacle you want to come down *NOW*.

Nothing applies to every airplane--and the AFH might be OK--but in the end I try things in real life and the result of my tests is how I fly that airplane. Sometimes I can beat the POH, sometimes the POH beats me.

 

[dmccormack]

I don't get what you're saying. You just got done saying all the extra flaps equals more drag. Now you're saying adding more flaps suddenly makes you float further.

The A36 is a low wing. The Low wing is well within ground effect. The A36 only has 15 or 20 degrees of flaps (not 30 or 40, which add lots of drag with very little increase in lift).

If you are fast (not on the correct airspeed for that airplane at it's current weight), you will float, period.

Kent is a friendly pilot that wants to help out GA. If ATC asks for you to keep it fast on final they generally are trying to get you out of the way for an airliner. Flying it in fast and landing it short off on the first taxiway makes room for that airliner behind you.

Kent also wants to be able to put a plane down safely in very little runway as he sometimes goes to airports with very little runway. In order to maximize every dollar spent--he often does this on longer runways.

I'm very glad.

Though most fields I've flown into with airline traffic have High Speed taxiways, and they are not right by the numbers.

You are very wrong. With more drag *you will* land shorter. You will slow faster in the air and you can slow to an airspeed that you can't easily climb at. On a real short field I keep a reasonable amount of airspeed to permit go arounds until short short final. At that point I dump all my excess airspeed and down I come.

The total landing distance is a function of distance flown in the roundout PLUS ground roll.

Sorry, but 1.3 Vso is 1.3 Vso, period.

Once rolling on the ground, putting the flaps up helps transfer weight from the wings to the wheels, thus increasing friction, thus reducing ground roll.

 

[poadeleted20]

The A36 is a low wing. The Low wing is well within ground effect. The A36 only has 15 or 20 degrees of flaps (not 30 or 40, which add lots of drag with very little increase in lift).

You want to check that against the A36 POH? I think you'll find that full flaps (the Landing position) is in fact 30 degrees, and that it is the Takeoff/Approach position which is only 15 degrees. I've only got 50 or 60 hours in the 36 model, so I could be wrong, but that's what I remember.

 

[jesse]

The A36 is a low wing. The Low wing is well within ground effect. The A36 only has 15 or 20 degrees of flaps (not 30 or 40, which add lots of drag with very little increase in lift).

If you are fast (not on the correct airspeed for that airplane at it's current weight), you will float, period.

Okay. I'll admit my A36 experience is lacking. But when I did fly the A36 it seemed pretty damn easy to me. Slow it down, toss some gear, add some flaps, land. I don't think that flaps are going to make you land longer. That is all

The total landing distance is a function of distance flown in the roundout PLUS ground roll.

Sorry, but 1.3 Vso is 1.3 Vso, period.

Once rolling on the ground, putting the flaps up helps transfer weight from the wings to the wheels, thus increasing friction, thus reducing ground roll.

1.3 Vs0 is 1.3 Vs0? Okay? You don't maintain 1.3 Vs0 until your wheels touch the runway. You slow in the final stages of the landing including the flare.

It's quite simple Dan, the more drag you have, the faster you'll slow from your 1.3 Vs0 to your touchdown speed. The faster you slow, the less distance, the shorter the landing.

 

[poadeleted20]

As a point of aerodynamics, it is not the flap setting alone which determines the descent angle at a given speed, but a combination of flap setting and power. Thus, you can get a steeper descent clean with no power than at full flaps with a lot of power. Of course, at the same power setting (like flight idle), you get a steeper descent with full flaps than no flaps, which is why you use full flaps for a short landing over an obstacle. But all things being equal, descent gradient is much better managed by power than by flap setting.

 

[jesse]

As a point of aerodynamics, it is not the flap setting alone which determines the descent angle at a given speed, but a combination of flap setting and power. Thus, you can get a steeper descent clean with no power than at full flaps with a lot of power. Of course, at the same power setting (like flight idle), you get a steeper descent with full flaps than no flaps, which is why you use full flaps for a short landing over an obstacle. But all things being equal, descent gradient is much better managed by power than by flap setting.

I agree. You can come in completely power off and make a landing just as short. I'm not that perfect though, so I add more drag then I need at that phase and make up for it with power. Too low, add more, too high take some out.

 

[poadeleted20]

You can fly 1.3 Vso in a Cessna with 20 degrees flaps.

True, but your stall margin will be reduced in comparison with flying 1.3 Vs0 with 40 flaps since stall speed at 20 flaps is higher, and Vs0 is, by definition, with full flaps (40 or 30, depending on the model year of, or mods to, the 172).

 

[poadeleted20]

I agree. You can come in completely power off and make a landing just as short. I'm not that perfect though, so I add more drag then I need at that phase and make up for it with power. Too low, add more, too high take some out.

Just how they do it landing on carriers.

 

[dmccormack]

True, but your stall margin will be reduced in comparison with flying 1.3 Vs0 with 40 flaps since stall speed at 20 flaps is higher, and Vs0 is, by definition, with full flaps (40 or 30, depending on the model year of, or mods to, the 172).

IIRC the stall speed difference between 20 and 40 degrees is 1 knot.

 

[dmccormack]

You want to check that against the A36 POH? I think you'll find that full flaps (the Landing position) is in fact 30 degrees, and that it is the Takeoff/Approach position which is only 15 degrees. I've only got 50 or 60 hours in the 36 model, so I could be wrong, but that's what I remember.

I have about 150 in an A36, but I'll double check tonight.

 

[dmccormack]

Okay. I'll admit my A36 experience is lacking. But when I did fly the A36 it seemed pretty damn easy to me. Slow it down, toss some gear, add some flaps, land. I don't think that flaps are going to make you land longer. That is all

What did I say?

You need to have the airspeed nailed in an A36 when landing full flaps or you will float.

The increased lift (due to flaps) coupled with ground effect (low wing) will cause the airplane to float.

 

[jesse]

The increased lift (due to flaps) coupled with ground effect (low wing) will cause the airplane to float.

Okay? The increased lift will also allow you to fly slower. Just because some people can't figure out how to control their airspeed isn't an excuse for not using all their flaps in the A36.

More lift, equals slower flight, equals shorter landing.
More drag equals faster deceleration equals shorter landings.
Flaps equal shorter landing.

I'm not sure what you're trying to point out. Are you trying to say that it lands shorter without flaps? If so, that's news to me, but I can't really argue that as I don't have much for A36 experience.

 

[dmccormack]

Okay? The increased lift will also allow you to fly slower. Just because some people can't figure out how to control their airspeed isn't an excuse for not using all their flaps in the A36.

More lift, equals slower flight, equals shorter landing.
More drag equals faster deceleration equals shorter landings.
Flaps equal shorter landing.

I'm not sure what you're trying to point out. Are you trying to say that it lands shorter without flaps? If so, that's news to me, but I can't really argue that as I don't have much for A36 experience.

I really have no idea what your question is or how it is derived from my previous post, but, I'll lay out the whys/wherefores of airspeed as a critical component of landing distance in an A36.

Target Airspeed in an A36 loaded normal (not gross) is 78 KIAS (1.3 Vso)

Assume:

• Same configuration -- flaps down to second position (only 2 positions in an A36), Gear down, Prop full forward
• Same power -- 13" MAP
• Same attitude -- nose up approx 8-9 degrees

If your airspeed is 90, rather than 78, you will land further down the runway, period -- flaps or no flaps.

Why?

• Ground effect -- the effective wing is closer to the runway when the flaps are down than up. Closer to the runway equals greater ground effect, thus canceling out a benefit of flaps.
• Increased Lift -- Flaps increase lift. More lift equals the airplane continues flying at a slower airspeed, which means the airplane will continue to fly when it could have stopped flying and landed.

The advantage of flaps is it allows us to continue flying the airplane at slower speeds, thus reducing the total energy at touchdown.

That is a good thing.

But "dumping flaps" and yelling "Whoa Boy" won't be as effective as controlling airspeed, and getting it right at 1.3 Vso (1.2 Vso would be better, but most pilots are uncomfortable with the little margin)

Aerodynamics for Naval Aviators posits that a 10% increase in airspeed results in a 21% longer total landing distance -- and landing distance is a function of roundout distance PLUS ground roll.

 

[jesse]

I really have no idea what your question is or how it is derived from my previous post, but, I'll lay out the whys/wherefores of airspeed as a critical component of landing distance in an A36.

Target Airspeed in an A36 loaded normal (not gross) is 78 KIAS (1.3 Vso)

Assume:

• Same configuration -- flaps down to second position (only 2 positions in an A36), Gear down, Prop full forward
• Same power -- 13" MAP
• Same attitude -- nose up approx 8-9 degrees

If your airspeed is 90, rather than 78, you will land further down the runway, period -- flaps or no flaps.

Why?

• Ground effect -- the effective wing is closer to the runway when the flaps are down than up. Closer to the runway equals greater ground effect, thus canceling out a benefit of flaps.
• Increased Lift -- Flaps increase lift. More lift equals the airplane continues flying at a slower airspeed, which means the airplane will continue to fly when it could have stopped flying and landed.

The advantage of flaps is it allows us to continue flying the airplane at slower speeds, thus reducing the total energy at touchdown.

That is a good thing.

But "dumping flaps" and yelling "Whoa Boy" won't be as effective as controlling airspeed, and getting it right at 1.3 Vso (1.2 Vso would be better, but most pilots are uncomfortable with the little margin)

Aerodynamics for Naval Aviators posits that a 10% increase in airspeed results in a 21% longer total landing distance -- and landing distance is a function of roundout distance PLUS ground roll.

Okay. I think we're on the same page. The flaps *if* you take advantage of them by flying slower *will* result in a shorter landing.

As far as dumping all the flaps at once? I don't see what you're trying to get at. Dump them whenever you feel like dumping them. The important thing, the only thing that matters, is that you have as little energy left in the wings as possible when the wheels touch the pavement.

 

[dmccormack]

Okay. I think we're on the same page. The flaps *if* you take advantage of them by flying slower *will* result in a shorter landing.

As far as dumping all the flaps at once? I don't see what you're trying to get at. Dump them whenever you feel like dumping them. The important thing, the only thing that matters, is that you have as little energy left in the wings as possible when the wheels touch the pavement.

Then we are in violent agreement -- but -- and a very qualified but -- too often pilots use flaps on short final with more hope than technique applied.

The reasoning is "Flaps will slow me down."

Well, sorta.

Better to determine the airspeeds for the airplane you're flying, fly those airspeeds, and alter the configuration and power as appropriate to the conditions.

Hard and fast "I always do X" rules usually find a breaking point -- and usually when it's least expected.

 

[flyingcheesehead]

You carefully ignored the quote from the AFH....

Not really - PoA doesn't double-quote. I did provide the evidence that on the 182 it doesn't seem to make any difference.

116.2 hours in airplanes with 40 degrees of flaps in the last 4 months.

Does that count?

I dunno, were any of those 182's?

Though there is a limit switch, you run the risk of burning out the flap motor if you hold it past the full extension (especially if the limit switch died).

Even with detents, I'm still listening to the motor - Any switch or sensor can go defective, so I'd rather pop the breaker before...

Now you need to go around and the flap motor is shot.

Now what?

... that happens. And that's why a the ability to do a go-around at gross with full flaps (though only on a standard day) is a certification requirement. Yeah, performance is gonna suck, but if you're past the point of being able to go around, you just put it on the ground.

You'd better have your airspeed right on the money if you extend full flaps in an A36 or you will float yourself right on down the runway.

Ummm... Why? Partial flaps would be more of a reduction in drag than lift, so you'd float MORE.

Why would you put it on the numbers during an ILS?

The GS leads to the touchdown point -- not the numbers.

I dunno, force of habit. If vis is good, I see those big juicy numbers and I just gotta land on 'em. So yes, I do go below glideslope/PAPI/VASI with good vis. If it's really crappy, I'll keep the glideslope just in case.

I haven't seen an ILS equipped runway yet that was so short I needed to do short field technique after coming in to minimums -- that's just plain risky, and unnecessary.

Short field technique? I'm not doing what I consider "short field technique". I'm using normal-landing technique - For me, that means full flaps, normal-landing airspeed (80 mph), aim for the start of the pavement, flare, land, and barring any gustiness I'll hold the nosewheel off as long as I can and generally only use the brakes enough to slow down for a taxiway. I won't burn up my tires and brakes to make the first one unless there's fast traffic behind me, but I'll do some braking to make the second one if I'd have to add power to make the third.

That's more than fine -- but -- have you done all this flying and landing with CG loaded to aft limits?

No - It's basically impossible to load this airplane to aft limits. Even with just me and fuel, I'd have to put 443 pounds in the aft baggage to reach gross and that is just barely past the aft limit - However, there's a max of 120 pounds allowed in the aft baggage compartment. If I load the baggage compartment to that limit and fill the rear seat to gross, I'm only about 2/3 of the way back. If I go to the extreme of pulling all but an hour of fuel out, loading aft baggage to the far aft limit, and filling the rear seat until gross, again it's only barely out of limits. But, I don't even land with an hour of fuel, much less ever take off with it. (One of my very few personal minimums is to never have under an hour in the tanks.)

Keep in mind -- while I am also a proponent of minimal speed landings, I can't accept that 40 degrees is required every single time.

It's not.

I'm not saying that either, I just am saying that I don't know of any scenarios where I wouldn't use them.

You can fly 1.3 Vso in a Cessna with 20 degrees flaps. The only advantage to 40 degrees over 20 or 30 is a steeper descent angle for the same airspeed, period. You don't land any slower, you don't land any shorter (in fact to decrease ground roll you should move flaps up so the wheels can create friction).

On a short-field landing in the Cessna, the flaps take so long to go up that there is no lift being developed by the time they're up. Leave 'em down to get the aerodynamic drag in the beginning of the landing roll, which allows you to pull the yoke harder earlier and thus get more friction on the mains. (I'll challenge you to a contest on that one any time. )

The A36 is a low wing. The Low wing is well within ground effect. The A36 only has 15 or 20 degrees of flaps (not 30 or 40, which add lots of drag with very little increase in lift).

The A36, like all Bonanzas, has 30 degrees of flaps.

If you are fast (not on the correct airspeed for that airplane at it's current weight), you will float, period.

That's true of any airplane. You gave the 78 vs. 90 knots example - Heck, even the C182 High-Wing Drag-O-Matic will float forever if you're 12 knots fast.

Though most fields I've flown into with airline traffic have High Speed taxiways, and they are not right by the numbers.

Hmmm. We don't have 'em. I flew into Midway over the weekend and they don't either. In fact, I don't know if I've ever flown to a field that did.

Once rolling on the ground, putting the flaps up helps transfer weight from the wings to the wheels, thus increasing friction, thus reducing ground roll.

Again, this really only works with manual flaps - The electric ones are too slow coming up to have much of an effect.

 

[dmccormack]

Hmmm. We don't have 'em. I flew into Midway over the weekend and they don't either. In fact, I don't know if I've ever flown to a field that did.

You need to get out more.