Full Flaps on Landing... Always?

[N1347B]

Seconded. After all, where else would you get more column ideas?

Shhhhhh!

Deb

 

[gismo]

So to boil it down to a short story, the difference in stall speed between flaps 25 and flaps 40 is minimal so I am currently setting flaps 25 for most of my landings. As always, everyone elses' mileage will vary...

On most airplanes the first half of the available flap deflection provides considerably more than half the stall speed reduction and considerably less than half the full flap drag increase. But there's a big advantage in having that extra drag in the flare and touchdown in that it reduces the time spent when you're most susceptible to wind changes. I always use full flaps unless I'm landing out of an ILS approach to mins in low visibility where dropping the last half of flaps can be a bit too destabilizing for my taste.

As to the trimming during the flare, I don't need to in my Baron but I do use a LOT of nose up trim on short final. OTOH, I can remember landing a C182 with two folks in front and no baggage and finding that it required a fairly hefty pull unless I rolled in more trim in the flare so this probably varies by type. In any case, unless your arm strength is rather limited, you shouldn't have any trouble keeping the nose off the ground at touchdown without trimming in the flare, trimming just makes it take less effort. I have found that it's not unusual for pilots to limit their force on the controls to a lot less than they are capable of.

 

[gismo]

1 Reduced elevator effectiveness with full flaps.

2 High sink rate on final at airports with gusty winds(Avalon comes to mind).

I don't fly a Cessna 172, so can't comment on that. In an early Bonanza with load at forward CG, full flaps will run out of elevator at 1.3VsO approach when the power is off. Bad mojo.

YMMV.

I have flown several Bonanzas loaded at or near the forward CG limit and can hold the nose off the ground with full flaps without difficulty. The only similar issue I ever encountered was on a E35 (v-tail) where the mixer reduced the available rudder when the wheel was held all the way back making crosswind soft field landings more difficult (but still possible). And IMO, there's just no way that any certified GA airplane without a stick pusher will preclude a stall with full up elevator and full flaps let alone have insufficient elevator to hold the nose up at 1.3 Vso and at the forward CG limit. I'm pretty certain that either the early Bonanza you flew has the CG further forward than you think, there's something wrong with it's rigging, or you weren't using all the elevator available.

Also that "high sink rate" can be eliminated by carrying more power.

 

[flyingcheesehead]

The thoery on higher speed in gusts is if the gust stops and you are flying into the wind the plane may fly like a rock. The higher air speed is a margin for safety, i.e. the increase your speed by 50% of the gust.

I agree, half the gust factor should be added. However, I think to be truly accurate it should be half the gust factor of the headwind component - The crosswind component isn't going to cause you to fall out of the sky.

The theory on cross winds is that at slower speeds the wind has more time to act on the aircraft therefore a larger effect.

Huh? The relative wind will be at a greater angle at a slower airspeed. But unless it's at enough of an angle and at a high enough magnitude to cause you to be running out of rudder, there's no reason to increase airspeed. And like I said before, if the crosswind is so high that you're actually hitting the stop on the rudder, you should probably be going elsewhere.

 

[docmirror]

I have flown several Bonanzas loaded at or near the forward CG limit and can hold the nose off the ground with full flaps without difficulty.

Also that "high sink rate" can be eliminated by carrying more power.

You're a much better pilot than me.

More power kind of defeats the purpose of full flaps. Kind of a cross purposes.

 

[LearDriver]

In the 737, Gulfstream and Lear we will adjust in an additive to ref speed if there is heavy wind down the runway, crosswind or wind shear reported. We assume heavy wind to be 10 knots or above. The additive is 1/2 the steady wind velocity and all the gust. We will cap the additive at different values for the different airplanes. The 737 and the Gulfstream are caped at 20 knots. The lear is capped at 15 knots. Thats only to give a buffer because on that airplane 20 knots is right at the final flaps limitation speed.

I apply this same additive to a 421 and a dakota that I fly. With these two airplanes I cap the additive at 10 knots extra. I find that it works really well.

 

[jesse]

You're a much better pilot than me.

Lance is a hell of a pilot. No joke .

 

[Clark1961]

As to the trimming during the flare, I don't need to in my Baron but I do use a LOT of nose up trim on short final. OTOH, I can remember landing a C182 with two folks in front and no baggage and finding that it required a fairly hefty pull unless I rolled in more trim in the flare so this probably varies by type. In any case, unless your arm strength is rather limited, you shouldn't have any trouble keeping the nose off the ground at touchdown without trimming in the flare, trimming just makes it take less effort. I have found that it's not unusual for pilots to limit their force on the controls to a lot less than they are capable of.

There are some physical issues with high control forces for just about all people. We humans are much more accurate in our movements when loads are small. My flares are much better when I can do them with my fingers and wrist rather than my arm.

The next issue is timing. Flying a 75 knot approach with flaps 40 and power off puts the Dakota into a pretty good nose down attitude. Getting a smooth nose high touchdown and holding the nose up after touchdown requires rather precise timing. The timing doesn't have to be quite so precise with flaps 25. Of course power can be carried all the way to touchdown and then the attitude change isn't so severe but I generally pull power when making the runway is assured and I commit to landing. I have this silly notion that power at touchdown is cheating. I also have another silly notion that landing short because I was depending on power would be pretty embarrassing. I watch folks fly exceptionally shallow approaches to land on the numbers of a 5,000 ft or longer runway and wonder what, exactly, they are thinking. Maybe I'm ruined as a pilot by learning to fly from an old Stearman driver.

As you typed, all aircraft have their own characteristics and those characteristics can change with CG and gross weight. Crosswinds must be dealt with and that demands that control is maintained while transitioning from flying to rolling. The keys are probably along the lines of know the aircraft and one's abilities and stay well within both. We should probably remember that cross-country is between airports, not off the runway...

 

[poadeleted20]

Floating in any plane means you're "too fast."

So, 1.3 Vso in the mooney comes out to 83.4 mph. The book recommends 80 mph on short final. Yep, do that and there's still float.

What's your gross weight at that point? Remember that you must reduce those speeds by the square root of the gross weight. In most light singles, reducing approach speed by one knot for every 100 lb below max gross is a good approximation. Thus, when I'm solo in my Tiger with half tanks, I need to slow about 6 knots below book approach speed. Since stall speed is also reduced, I still have the same stall margin, and avoid the float.

 

[poadeleted20]

The thoery on higher speed in gusts is if the gust stops and you are flying into the wind the plane may fly like a rock. The higher air speed is a margin for safety, i.e. the increase your speed by 50% of the gust.

That's fine, but don't reduce your flap setting or you'll negate the effect of the increased speed.

 

[poadeleted20]

Or simply add S turns on final as needed and land, especially where go around is not an option.

If go-around is not an option, plan your approach so a go-around is not required (to paraphrase the section in the C-5 flight manual on three-engine-inoperative approaches).

 

[poadeleted20]

In the 737, Gulfstream and Lear we will adjust in an additive to ref speed if there is heavy wind down the runway, crosswind or wind shear reported. We assume heavy wind to be 10 knots or above. The additive is 1/2 the steady wind velocity and all the gust. We will cap the additive at different values for the different airplanes. The 737 and the Gulfstream are caped at 20 knots. The lear is capped at 15 knots. Thats only to give a buffer because on that airplane 20 knots is right at the final flaps limitation speed.

The far greater sectional density (ratio of mass to surface area) of those jets creates a very different response to gusts and shears. In those airplanes, you can see large drops in airspeed when passing the shear level or being hit by a gust. In the kites most of us here fly, all you feel is a bump and all you see is a quick flick of the airspeed indicator when passing the shear level -- the difference between a leaf and a rock passing through the air.

 

[wabower]

Which Gulfsteam?

In the 737, Gulfstream and Lear we will adjust in an additive to ref speed if there is heavy wind down the runway, crosswind or wind shear reported. We assume heavy wind to be 10 knots or above. The additive is 1/2 the steady wind velocity and all the gust. We will cap the additive at different values for the different airplanes. The 737 and the Gulfstream are caped at 20 knots. The lear is capped at 15 knots. Thats only to give a buffer because on that airplane 20 knots is right at the final flaps limitation speed.

I apply this same additive to a 421 and a dakota that I fly. With these two airplanes I cap the additive at 10 knots extra. I find that it works really well.

 

[LearDriver]

Which Gulfsteam?

G-III

 

[docmirror]

Lance is a hell of a pilot. No joke .

Do you see me laughing?

 

[brcase]

I can really only come up with two reasons not to use full flaps.

1. Small Cessnas don't climb very well with full flaps. If the need for a go-around arises and the flaps don't come up (which is pretty unlikely, but not impossible), that's not so good.

2. Passenger comfort. Steep approaches spook some people.


Trapper John

Another one for me being a bit of an efficiency nut it makes little sense to apply full flaps and then add power to compensate for the drag you just added. I equate it to driving you car with the parking brake on. I just add the flaps when I need them. I frequently land 172’s power off no flaps, 182’s and larger I will add 10 degree for trim.

Also as noted, some airplanes are easier to land with partial flaps. My sailplane has 90 degree flaps, I seldom land it full flaps, it’s glide ratio goes to 2:1 with full flaps.

Brian

 

[wabower]

Does the book for that one use a calculated VAPP (Vref + a fudge or are the TOLD card numbers strictly based on Ref?

G-III

 

[flyingcheesehead]

In the 737, Gulfstream and Lear we will adjust in an additive to ref speed if there is heavy wind down the runway, crosswind or wind shear reported. We assume heavy wind to be 10 knots or above. The additive is 1/2 the steady wind velocity and all the gust.

Hmmm. I don't understand why you'd add half the steady wind. With a strong headwind on final, you'd need more power to maintain the same glide angle relative to the earth because you'd need a shallower glide angle relative to the air, but what benefit does adding half the steady wind give you? It seems you would just float a bit more on landing, though with a lot of headwind that wouldn't be an issue because the wind would cancel out the extra runway that you floated past most likely.

But, like Ron says:

The far greater sectional density (ratio of mass to surface area) of those jets creates a very different response to gusts and shears. In those airplanes, you can see large drops in airspeed when passing the shear level or being hit by a gust. In the kites most of us here fly, all you feel is a bump and all you see is a quick flick of the airspeed indicator when passing the shear level -- the difference between a leaf and a rock passing through the air.

So...

I apply this same additive to a 421 and a dakota that I fly. With these two airplanes I cap the additive at 10 knots extra. I find that it works really well.

It seems that in gusty conditions, especially with the Dakota, you'd be asking to be picked back up off the runway and dropped if you add half the steady wind and all the gust factor.

 

[LearDriver]

Hmmm. I don't understand why you'd add half the steady wind. With a strong headwind on final, you'd need more power to maintain the same glide angle relative to the earth because you'd need a shallower glide angle relative to the air, but what benefit does adding half the steady wind give you? It seems you would just float a bit more on landing, though with a lot of headwind that wouldn't be an issue because the wind would cancel out the extra runway that you floated past most likely.

But, like Ron says:



So...



It seems that in gusty conditions, especially with the Dakota, you'd be asking to be picked back up off the runway and dropped if you add half the steady wind and all the gust factor.

Those additives are above ref speed not touchdown speed.

 

[bobmrg]

Two words that pilots...especially instructors...should think long and hard before using: "always" and "never."

Bob Gardner

 

[dmccormack]

Two words that pilots...especially instructors...should think long and hard before using: "always" and "never."

Bob Gardner

I never doubt you, Bob -- you're always right!

:wink2:

(Snideness aside -- excellent point!)

 

[Clark1961]

It seems that in gusty conditions, especially with the Dakota, you'd be asking to be picked back up off the runway and dropped if you add half the steady wind and all the gust factor.

It's easy to bleed off 10 knots extra in the Dakota...it'll float a bit if ya don't pull the power off soon enough but if done right the 10 knots extra won't even be noticed by anyone but the pilot.

Now if one is foolish enough to allow the aircraft to alight 10 knots fast then it's a whole different ballgame...

 

[jesse]

It's easy to bleed off 10 knots extra in the Dakota...it'll float a bit if ya don't pull the power off soon enough but if done right the 10 knots extra won't even be noticed by anyone but the pilot.

Now if one is foolish enough to allow the aircraft to alight 10 knots fast then it's a whole different ballgame...

So if you have to bleed that 10 knots off to land--why would you want to bleed that off in close proximity to the ground while burning up excess runway?

Too much speed and a lot of wind is a really good way to mess up an airplane. They just don't do better with excess speed in the landing phase.

 

[Clark1961]

So if you have to bleed that 10 knots off to land--why would you want to bleed that off in close proximity to the ground while burning up excess runway?

Too much speed and a lot of wind is a really good way to mess up an airplane. They just don't do better with excess speed in the landing phase.

It's fairly easy to dump the 10 knots in the round out - just start a bit high. Now if you don't do that then it'll be a bad situation. I agree with you totally: don't invite float and don't land fast.

 

[poadeleted20]

It's fairly easy to dump the 10 knots in the round out - just start a bit high.

I've seen that technique end with the nosewheel retracted (on a fixed gear airplane) or the main wheel struts sticking through the wings.

 

[Clark1961]

I've seen that technique end with the nosewheel retracted (on a fixed gear airplane) or the main wheel struts sticking through the wings.

That all depends on what a "bit" is now doesn't it?

The gust factor has to be bled off somewhere. Where do you want to do it?

 

[Keith Lane]

I tend to agree with this. Especially with a 172 with the 40 degree flaps. I don't like to go beyond 30 degrees unless its needed for a short field.

I don't understand that thought process....I want to land as slow as I can. If I could land with 80 degree flaps at 20knots, I'd do it. lol

I've got 40°, and I use them if I need them. I typically use 30°, though. For me, if you need to go around, after power is applied on the go around, you had better get those last 10° back in pretty quick as it just hates flying under power with all 40° out there. Add this to the type of flap switch I have, which you can flip up and have it stay up, can make things get interesting in a hurry, dumping more flaps than you really want. If I'm doing a go around, things are probably interesting enough already for me.

 

[wabower]

I've got 40°, and I use them if I need them. I typically use 30°, though. For me, if you need to go around, after power is applied on the go around, you had better get those last 10° back in pretty quick as it just hates flying under power with all 40° out there. Add this to the type of flap switch I have, which you can flip up and have it stay up, can make things get interesting in a hurry, dumping more flaps than you really want. If I'm doing a go around, things are probably interesting enough already for me.

What determines when you "need them"?

Does your POH address going around with full flaps?

Is the airplane that hates it, or the pilot that's not happy doing it?

What is the primary difference in your "interesting enough" activities with 30 vs. 40 degrees?

Have you compared results (at a safe altitude) to determine the difference between the two settings insofar as flying a complete pattern back to another landing with flaps deployed?

 

[gismo]

Another one for me being a bit of an efficiency nut it makes little sense to apply full flaps and then add power to compensate for the drag you just added. I equate it to driving you car with the parking brake on. I just add the flaps when I need them. I frequently land 172’s power off no flaps, 182’s and larger I will add 10 degree for trim.

Also as noted, some airplanes are easier to land with partial flaps. My sailplane has 90 degree flaps, I seldom land it full flaps, it’s glide ratio goes to 2:1 with full flaps.

Brian

Landing isn't about efficiency, if that were the case we'd use 0 flaps and wait till the last possible second to lower the gear. I normally drop full flaps at 300-500 agl and the effect on the flight's efficiency is likely too small to measure.

As to the comment about adding power to compensate for full flaps, you have to start from the point of view that full flaps provide a safety and wear benefit and then proceed to the methodology that allows the use of full flaps without increasing the glide angle above what's desired (by adding power).

For your automobile analogy, the closest thing would be the technique of applying simultaneous power and brakes in a turn to control a car's attitude and to keep boost up coming out of a turn. That's not efficient either but it's very effective at shifting the car's balance forward and aft and/or increasing the power available at the conclusion of a turn.

 

[Skip Miller]

For your automobile analogy, the closest thing would be the technique of applying simultaneous power and brakes in a turn to control a car's attitude and to keep boost up coming out of a turn. That's not efficient either but it's very effective at shifting the car's balance forward and aft and/or increasing the power available at the conclusion of a turn.

Another automotive example, there are several flavors of traction control systems in automobiles that keep the rubber attached to the road by applying one or more of the wheel brakes at the appropriate time by computer. That is not efficient in terms of MPG but it may be very efficient in terms of time outside the body shops.

-Skip

 

[dmccormack]

Another automotive example, there are several flavors of traction control systems in automobiles that keep the rubber attached to the road by applying one or more of the wheel brakes at the appropriate time by computer. That is not efficient in terms of MPG but it may be very efficient in terms of time outside the body shops.

-Skip

...motorcyle analogy: Roll off throttle in turn, roll on throttle from apex on.

Weight shifts, wheel spins, turn carved.

I have no idea how this applies to flaps.

 

[Keith Lane]

What determines when you "need them"?

I use them primarily when I want to make a fairly steep approach, and keep my speed at 70-75 MPH. At the flare, speed falls off very quickly with touchdown at 60 or slightly less.

SHORT FIELD LANDING
1. Airspeed - 70-80 (flaps up)
2. Flaps - 40 ° down below 100 mph
3. Airspeed - 69 until flare
4. Touchdown - MAINS FIRST
5. Brakes - APPLY HEAVILY
6. Flaps - RETRACT


Does your POH address going around with full flaps?

Yes, after applying full power, retract flaps to 20°.

BALKED LANDING
1. Throttle - FULL OPEN
2. Carb Heat - COLD
3. Flaps - RETRACT to 20 °
4. Climb Speed - 65 until reaching a safe altitude
5. Flaps - RETRACT slowly at a safe altitude



Is the airplane that hates it, or the pilot that's not happy doing it?

Both. It's pretty hard to establish a decent positive rate of climb even at WOT with 40° out there. Also yoke forces get pretty heavy (for a 172 ).

What is the primary difference in your "interesting enough" activities with 30 vs. 40 degrees?

Yoke forces, amount of trim to combat same. The "interesting enough" refers to something in the landing phase that has interrupted an otherwise "normal" approach and precipitates the need for some action. I suppose that once the need has appeared, and the go-around is committed to, the cause for the go-around is no longer the issue, but executing the go-around is the only focus. I have inadvertently raised the flaps all the way by batting the flap switch up, where it will stay until you re-center it. This was on a long runway, during a practice rejected landing, and not realizing why I was sinking took a few seconds. I got too busy trimming and pushing, etc. This was some time ago, after only owning the plane a few months. I've had it 12+ years now, and that probably would not happen today.

Have you compared results (at a safe altitude) to determine the difference between the two settings insofar as flying a complete pattern back to another landing with flaps deployed?

Actually, no. I have practiced go arounds, typically with an instructor onboard, with both 30° and 40 ° deployed.

 

[wabower]

Good answers. Almost as good as if they had been written by a train guy rather than an engine guy.:wink2:

I think the airplane had to be able to do the rejected landing and return with the flaps at 40 for certification, but would defer to those who know that stuff.

What determines when you "need them"?

I use them primarily when I want to make a fairly steep approach, and keep my speed at 70-75 MPH. At the flare, speed falls off very quickly with touchdown at 60 or slightly less.

SHORT FIELD LANDING
1. Airspeed - 70-80 (flaps up)
2. Flaps - 40 ° down below 100 mph
3. Airspeed - 69 until flare
4. Touchdown - MAINS FIRST
5. Brakes - APPLY HEAVILY
6. Flaps - RETRACT


Does your POH address going around with full flaps?

Yes, after applying full power, retract flaps to 20°.

BALKED LANDING
1. Throttle - FULL OPEN
2. Carb Heat - COLD
3. Flaps - RETRACT to 20 °
4. Climb Speed - 65 until reaching a safe altitude
5. Flaps - RETRACT slowly at a safe altitude



Is the airplane that hates it, or the pilot that's not happy doing it?

Both. It's pretty hard to establish a decent positive rate of climb even at WOT with 40° out there. Also yoke forces get pretty heavy (for a 172 ).

What is the primary difference in your "interesting enough" activities with 30 vs. 40 degrees?

Yoke forces, amount of trim to combat same. The "interesting enough" refers to something in the landing phase that has interrupted an otherwise "normal" approach and precipitates the need for some action. I suppose that once the need has appeared, and the go-around is committed to, the cause for the go-around is no longer the issue, but executing the go-around is the only focus. I have inadvertently raised the flaps all the way by batting the flap switch up, where it will stay until you re-center it. This was on a long runway, during a practice rejected landing, and not realizing why I was sinking took a few seconds. I got too busy trimming and pushing, etc. This was some time ago, after only owning the plane a few months. I've had it 12+ years now, and that probably would not happen today.

Have you compared results (at a safe altitude) to determine the difference between the two settings insofar as flying a complete pattern back to another landing with flaps deployed?

Actually, no. I have practiced go arounds, typically with an instructor onboard, with both 30° and 40 ° deployed.

 

[Clark1961]

I think the airplane had to be able to do the rejected landing and return with the flaps at 40 for certification, but would defer to those who know that stuff.

I think the cert is to do the rejected landing with full flaps, at max gross, at sea level. The sea level bit is sorta important. I believe that is why the turbo Dakota I fly has a 100 lb lower max gross than the normally aspirated version.

 

[poadeleted20]

I think the airplane had to be able to do the rejected landing and return with the flaps at 40 for certification, but would defer to those who know that stuff.

They do -- at sea level, standard day, max gross, and then not necessarily if you can meet that two-second rule in subparagraph (3) (although I don't think a C-172 can -- big pitch change required).

Section 23.77: Balked landing.

(a) Each normal, utility, and acrobatic category reciprocating engine-powered airplane at 6,000 pounds or less maximum weight must be able to maintain a steady gradient of climb at sea level of at least 3.3 percent with—
(1) Takeoff power on each engine;
(2) The landing gear extended;
(3) The wing flaps in the landing position, except that if the flaps may safely be retracted in two seconds or less without loss of altitude and without sudden changes of angle of attack, they may be retracted; and
(4) A climb speed equal to VREF, as defined in §23.73(a).

However, move the DA up, and all bets are off.

 

[flyingcheesehead]

I think the cert is to do the rejected landing with full flaps, at max gross, at sea level. The sea level bit is sorta important. I believe that is why the turbo Dakota I fly has a 100 lb lower max gross than the normally aspirated version.

Probably - At sea level, the Dakota is making 235 hp while the Turbo Dakota maxes at 200. I have no idea why Piper decided to lower the hp on the turbo version, that's pretty unusual.

 

[Skip Miller]

Probably - At sea level, the Dakota is making 235 hp while the Turbo Dakota maxes at 200. I have no idea why Piper decided to lower the hp on the turbo version, that's pretty unusual.

What horsepower is the NA Dakota making at sea level full static rpm? Just curious...

-Skip

 

[Pilawt]

Probably - At sea level, the Dakota is making 235 hp while the Turbo Dakota maxes at 200. I have no idea why Piper decided to lower the hp on the turbo version, that's pretty unusual.

"Turbo Dakota" is an unfortunate and misleading name for the PA-28-201T, which is really nothing more than a Turbo Arrow III with fixed gear.

 

[Clark1961]

"Turbo Dakota" is an unfortunate and misleading name for the PA-28-201T, which is really nothing more than a Turbo Arrow III with fixed gear.

Ummm, by that standard a Dakota is nothing more than a 235 hp Arrow III with fixed gear. They're all P28B and share the same cert. If you don't believe me then look-up part numbers for significant airframe members...

 

[Dave Krall CFII]

<snip> I have inadvertently raised the flaps all the way by batting the flap switch up, where it will stay until you re-center it. This was on a long runway, during a practice rejected landing, and not realizing why I was sinking took a few seconds. I got too busy trimming and pushing, etc. This was some time ago, after only owning the plane a few months. I've had it 12+ years now, and that probably would not happen today.

<snip>

I quickly got to the point with students that if they didn't do one of those naturally by themselves (which they usually did) then I would "inadvertently" do a full flap retraction on a go around demo then fly and/or roll through the counter measures. It's safe, and a more effective teaching tool demonstrating lift and drag, than just verbalizing because it appears rather dramatic to them.