40deg flaps

<snip>

At flaps 40 a Cessna 150 or 172 is not a healthy bird. In event of a balked landing drag is so great it ain’t gonna climb worth beans until flaps are milked up to 20. (If you gotta go around at flaps 40 what do you do if the flap motor quits?) On approach with flaps 20 the potential pilot workload is decreased and safety margin increased.

<snip>

Was rather happy I was not using full flaps the 3 times the flaps failed to retract on me last year. This was in 3 different C-172's.

Brian
 
I suspect the emoji there is supposed to clue the poor hapless poster into realizing the above is sarcasm. But in case he didn't catch it, THERE'S NO REASON NOT TO SLIP A 150 with full flaps.
There's darned little reason to even be concerned about it in certain 172 where some manuals advise against it.

I remember reading the caution about a forward slip with 40* flaps in certain 172s (early 172R I think). I thought is was a caution to be aware of it and not freak out. Not a prohibition against it. I actually went out and tried it a couple of times. We managed to get a bit wobble, that was about it. Certainly no violent loss of control or anything.
 
My Cub flaps drop to 70*. There have been a lot of times I wished my 180 had more than 40. Didn't Birddogs have 50*? Same wing.
A Birddog in military service has 60 deg. The same Birddog with an "N" number (Cessna 305) must be placarded to limit flaps to 40. They will still go down to 60, however. It now also requires a stall warning horn.
 
Was rather happy I was not using full flaps the 3 times the flaps failed to retract on me last year. This was in 3 different C-172's.

That usually happens during the G part of T&G.

My initial instructor drilled it into my head you have to look outside and confirm motion.

The first 150 I flew had the “hold the switch up or down for motion” version of Cessna controls so it was easier to drill the “don’t trust the Pre-selector” into my head later.

*Edit: Autocorrect turned Pre-selector into LTE-selector. LOL.
 
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There's a certification requirement for go around roc with full flaps -or- what can be retracted in a certain number of seconds. This is the reason many of the Cessnas got flap limits added.
 
I remember reading the caution about a forward slip with 40* flaps in certain 172s (early 172R I think). I thought is was a caution to be aware of it and not freak out. Not a prohibition against it. I actually went out and tried it a couple of times. We managed to get a bit wobble, that was about it. Certainly no violent loss of control or anything.
Slips with flaps

It’s not a myth, but it’s not a big deal, either.

Here’s what Bill Thompson, former Manager of Flight Test & Aerodynamics at Cessna, had to say about the issue of slipping with full flaps in the 172 (Cessna — Wings for The World, by William D. Thompson, Maverick Press, 1991, p. 41):

With the advent of the large slotted flaps in the C-170, C-180, and C-172 we encountered a nose down pitch in forward slips with the wing flaps deflected. In some cases it was severe enough to lift the pilot against his seat belt if he was slow in checking the motion. For this reason a caution note was placed in most of the owner’s manuals under “Landings” reading “Slips should be avoided with flap settings greater than 30 deg. due to a downward pitch encountered under certain combinations of airspeed, side-slip angle, and center of gravity loadings”. Since wing-low drift correction in crosswind landings is normally performed with a minimum flap setting (for better rudder control) this limitation did not apply to that maneuver. The cause of the pitching motion is the transition of a strong wing downwash over the tail in straight flight to a lessened downwash angle over part of the horizontal tail caused by the influence of a relative “upwash increment” from the upturned aileron in slipping flight. Although not stated in the owner’s manuals, we privately encouraged flight instructors to explore these effects at high altitude, and to pass on the information to their students. This phenomenon was elusive and sometimes hard to duplicate, but it was thought that a pilot should be aware of its existence and know how to counteract it if it occurs close to the ground.

The larger dorsal fin introduced on the 1972 C-172L apparently eliminated the issue.

These images illustrate the upwash from the upturned aileron encountering the horizontal stabilizer. In the first image the airplane is in coordinated flight; in the second it is in a slip to the left. In both images the airplane is tracking (in still air) toward the mountain peak in the distance.





There is a separate, unrelated phenomenon that Thompson described in newer models in full-flap slips: “a mild pitch ‘pumping’ motion resulting from flap outboard-end vortex impingement on the horizontal tail at some combinations of side-slip angle, power, and airspeed.” This is entirely benign and common with other high-wing airplanes. My Sport Cub did the same thing.

So although the 172L’s larger dorsal solved the pitch-down issue, they kept the cautionary note in the POH because of the latter phenomenon.

Unfortunately Cessna contributed to the “end of the world” fear of slips with flaps, by not explaining the phenomenon in the manuals; and in fact, many earlier C-172 manuals expressly said that slips with full flap were prohibited. I rummaged through my collection of old Cessna owners manuals:

1958 C-172: “prohibited”
1959 C-175: “prohibited”
1966 C-172F: “prohibited”
1972 C-172L (first year of the big dorsal): “should be avoided”
The manuals for these older models have been revised since then, and in fact the TCDS no longer carries the prohibition against slips with flaps. The POH for the current C-172S indicates that it's no biggie:
"Steep slips with flap settings greater than 20° can cause a slight tendency for the elevator to oscillate under certain combinations of airspeed, sideslip angle, and center of gravity loadings."

But a lot of us old-timers read the scary language in the old manuals back then and that's what we remember.
 
The '56 '57 manual I have also says "Prohibited"

Honestly with 40 degree flaps slipping shouldn't be necessary unless the whirly bit stops whirring and you need to get it in somewhere you need to do whatever is necessary at that point.

It would be interesting to compare 40 degrees of flaps vs 20 with a side slip.
 
The 150 becomes a manhole cover with 40*, ie it is coming straight down. Thing will stop in 200 ft if you have any wind but in the event of a go around, those big barn doors have to come up RIGHT NOW. Might take flying level to get enough smash to actually start climbing. So, go practice landings with all flap settings but realize 40* takes some careful flying in certain situations.

Hmmm, years ago I had a bunch of Champ time and then started flying a 150 with 40 degrees of flaps. Compared to slipping the Champ in to land, the 150 with 40 degrees of flap power off still felt "stuck" up in the air on approach like it wouldn't come down worth a damn, slip or no slip. There are a million airplanes that can be made to descend much steeper than a 150 with 40 flaps. It's all relative I guess. Then I started flying biplanes which made the Champ feel "stuck" in the air. ;)
 
...Compared to slipping the Champ in to land, the 150 with 40 degrees of flap power off still felt "stuck" up in the air ...

My experience as well. After getting my PPL in a 150, doing a fwd slip in a Champ was an eye-opener. Since then, I've flown other aircraft that take an extreme nose-down attitude to maintain airspeed in a fwd slip. In my little Sonerai, which doesn't have flaps, I can descend so steep, I can draw an audience from the inside hangar row.
 
My Cub flaps drop to 70*. There have been a lot of times I wished my 180 had more than 40. Didn't Birddogs have 50*? Same wing.

I learned to fly in a Supercub, owned part of a PA-12, and did some private flying in Piper Cherokee 140s, 161s and 180s. I never flew a C150 until I started my instrument and commercial work, and then I flew a C172 with 2 aboard before I flew a C150. That first C150 flight included an instructor who asked me to demonstrate a short field landing over an obstacle. I did it like I would in a Supercub, PA-12 or one of the much more moderately flapped Piper low wing singles - I did a full flap approach in level flight just over the "trees", then upon clearing them, actively pushed the nose over and about gave the instructor a heart attack as he cobbed on power and initiated the flare a lot higher than I would have. We bent the tail hold down ring slightly on the ensuing very tail low landing.

The moral here, and the thing I didn't fully appreciate or in some respects know on my first ever C150 flight, was that the C150 has much higher wing loading than a cub, and poor elevator authority at full flap with low airspeed. What the instructor had in mind was what is described below. What I had in mind was what worked with a large Cub wing with fairly small flaps. We had a major failure in communication about the actual procedure to be used.

Short runway, tall trees owned by the government a few hundred feet from the end of the runway. The other end of the runway abutted a railroad ROW with the rails 20 feet above the runway, and telegraph wires 30 feet above the runway.

All the local flying schools forbid students flying into College Park, KCGS, due to the number of accidents related to the obstructions.

Our standard approach from the tree end was 40 degrees of flaps, 10 MPH over stall, and just above idle, so the engine would respond quickly if you needed it. Cross 10 feet over the trees, engine to idle, drop the nose, and head for the numbers. Make a progressive flare, reaching level at a couple of feet about 200 feet down the runway, and slowly set it down, full stall, and hold the nose up for max air braking (We had Bendix brakes). When the nose came down, lightly brake, and turn off midfield. We did not come close to running off the end of the runway landing.

No flap approach, 7 MPH faster, flare a quarter of the way down the runway, settle in half way down, lower drag without flaps, so set the nose down, brake gently, and turn off at the end of the runway. Those tiny Bendix pucks wore out about once a month, so the no flaps landings accelerated replacement.

The difference in margin of runway length was immense, club rules were strong on preferring full flaps. Ground instruction also included the sequence of 40 to 20 flaps as soon as a go around started (Johnson bar), as soon as full throttle was applied and carb heat was off. Safe speed, 20 to 10, best angle of climb speed, and 10 to 0. Spare time in the sequence, the trim wheel spinning to take yoke forces off, to make flying easy, and assure no pitch up problems. With that carefully trained prior to actual flight, we had no problems.

About 20 guys learned to fly in our 150 with out any damage from trees or excursions from the runway, so the technique worked. All first solo's were at CGS, as the student would have to be proficient in getting home after solo practice. During the same time, the trees ate a 172 and a Beechcraft, and the railroad ate a Mooney flown by an ATP Airline pilot.

One of the advantages of 40, or 30 degrees of flaps, if the engine quits, just raise to 20, then 10, and the reduced drag greatly extends the distance/ height of your approach, and then when the runway is made, the flaps can be used again to reduce speed to get down near the beginning of the runway, making the whole runway available. This is particularly true with an engine failure, and fine tuning touchdown into a pasture close to the fence, at minimum speed.

I added the emphasis in italics above. I agree with you. Unfortunately, the FAA takes a fairly dim view of taking back flaps on an approach and landing. Doing that on a simulated engine out spot landing during a commercial checkride would probably be disqualifying.
 
Love slipping in the Champ. Don't hate me sometimes I come in high on purpose. :p
 
... Unfortunately, the FAA takes a fairly dim view of taking back flaps on an approach and landing. Doing that on a simulated engine out spot landing during a commercial checkride would probably be disqualifying.

And why would that be disqualifying? Unless you had to use the engine to make the spot, all else is available with perhaps the exception of pushing the examiner out the door to stretch the glide.
 
Unless you had to use the engine to make the spot, all else is available with perhaps the exception of pushing the examiner out the door to stretch the glide.

I know that was a joke (I hope!), but making a plane lighter does not increase its glide distance. In fact, with a headwind, it actually decreases it. Assuming one is maintaining the appropriate airspeed for the weight.
 
I know that was a joke (I hope!), but making a plane lighter does not increase its glide distance. In fact, with a headwind, it actually decreases it. Assuming one is maintaining the appropriate airspeed for the weight.

Just another reason pushing the DPE out the door would be considered poor form. I still haven't heard why decreasing the flap setting would be disqualifying. Has anyone gone to course pitch on the prop to decrease drag on the power off?
 
Has anyone gone to course pitch on the prop to decrease drag on the power off?
It doesn't work. The governor won't increase the prop pitch no matter what you do with the prop control when the engine is at idle or anywhere near it.
 
I know I am late to this thread but I like to configure the airplane for a go-around on final. That way if I have to abort all that I do is push in the throttle. So once up you line on final, shut off carb heat, then set flaps for best short field takeoff, and open the cowl flaps. You don't have cowl flaps on the 150 but you do have carb heat, so close that first. On my old Cherokee I'd use full flaps down to about 200 AGL then drop back to 2/3, the short field climb setting. The plane would sink about 50 feet and settle into a slightly shallower glide. The Cherokee climbs steeper and turns tighter on 2/3 flaps than any other setting. I also found it easier to control the pitch as the airplane slows and lands, especially when lightly loaded with more weight forward, like a solo flight with 1/3 fuel aboard. If the wind is up I top off the tanks to make the bird as heavy as possible so the wind gusts are less noticable. Hope this helps.

Have fun! Fly SAFE! petehdgs N1935Y
 
I know I am late to this thread but I like to configure the airplane for a go-around on final. That way if I have to abort all that I do is push in the throttle. So once up you line on final, shut off carb heat, then set flaps for best short field takeoff, and open the cowl flaps. You don't have cowl flaps on the 150 but you do have carb heat, so close that first. On my old Cherokee I'd use full flaps down to about 200 AGL then drop back to 2/3, the short field climb setting. The plane would sink about 50 feet and settle into a slightly shallower glide. The Cherokee climbs steeper and turns tighter on 2/3 flaps than any other setting. I also found it easier to control the pitch as the airplane slows and lands, especially when lightly loaded with more weight forward, like a solo flight with 1/3 fuel aboard. If the wind is up I top off the tanks to make the bird as heavy as possible so the wind gusts are less noticable. Hope this helps.

Have fun! Fly SAFE! petehdgs N1935Y

To each their own but this is terrible advice and if you do this on a BFR or check ride you will fail. For starters leave the carb heat on. It’s whole purpose is to prevent carb ice which is very likely in an O-200 and short final is the last place you want it. I’d rather have reduced climb performance should I chose to go around than no power. You should be fully configured once turning final and adjust your glide path of needed with throttle.

there isn’t a runway in the world that you would be going to in a 150 that doesn’t leave plenty of room for a go around even if needing to work out 40 degree flaps.
 
To each their own but this is terrible advice and if you do this on a BFR or check ride you will fail. For starters leave the carb heat on. It’s whole purpose is to prevent carb ice which is very likely in an O-200 and short final is the last place you want it. I’d rather have reduced climb performance should I chose to go around than no power. You should be fully configured once turning final and adjust your glide path of needed with throttle.

there isn’t a runway in the world that you would be going to in a 150 that doesn’t leave plenty of room for a go around even if needing to work out 40 degree flaps.
Very true, and the engine will respond better with warm induction air than with ambient temp air. Those little Continentals will ice up in a heartbeat when the conditions are right, and at idle in the glide air is driving the prop faster, making the MP lower, so the pressure drop at the throttle plate is huge, meaning that the temperature drop there is also huge, larger than on the ground at idle. A pilot closing the carb heat on final could find the engine weak or dead on the abort.

Younger pilots need to understand that POHs and AFMs and checklists are full of things learned the hard ways: injury and death.
 
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That’s a load of doo. The reason all the pilots I know who use carb heat push it off on final is to provide better power and throttle response for a go-around. I could tell two stories to illustrate that where carb heat on almost led to disastrous results. The standard procedure among pilots flying short strips is carb heat on for the approach and off on short final. That technique has withstood many a BFR.
 
That’s a load of doo. The reason all the pilots I know who use carb heat push it off on final is to provide better power and throttle response for a go-around. I could tell two stories to illustrate that where carb heat on almost led to disastrous results. The standard procedure among pilots flying short strips is carb heat on for the approach and off on short final. That technique has withstood many a BFR.
My CFI taught me to, on a go around, push both carb heat and throttle at the same time. On final, I have my hand on throttle and my thumb over carb heat so I can do that.
 
...making a plane lighter does not increase its glide distance.
That is so un-intuitive! I'm not a glider pilot, so maybe someone can help me with my thought experiment:

The Jolly Green Giant is standing in a field of beans with two identical model airplanes, one in each hand. Each has the same design, down to the last rivet, and are of the exact same size. Upon launch, which will glide farther, the one made from balsa and covered with tissue paper, or the one made from cast iron and covered with steel plate?​
 
That is so un-intuitive! I'm not a glider pilot, so maybe someone can help me with my thought experiment:

The Jolly Green Giant is standing in a field of beans with two identical model airplanes, one in each hand. Each has the same design, down to the last rivet, and are of the exact same size. Upon launch, which will glide farther, the one made from balsa and covered with tissue paper, or the one made from cast iron and covered with steel plate?​

Assuming both are flown at best glide speed for their weight...

The balsa plane will ever so slowly waft down, little by little, and eventually hit a certain distance away.

The iron/steel contraption will shoot down like a lawn dart, hitting the ground at exactly the same distance.

This assumes zero wind effects. If there is a headwind, lighter plane won’t glide as far, since it’s spending far more time in the headwind condition.

Note that in performance charts where weight affects performance, a certain weight is specified. Typically, glide distance/ratio charts don’t include weight, though the speed given for best glide can be assumed to be at max gross weight.
 
Never say never in aviation. The old Luscombe POH had a provision to add carb heat on T.O. if the fuel tank behind the pilot was half full.
 
Me, three.

I frankly have never heard of turning off carb heat on final. Not saying it isn’t a “thing”, just that I’ve never been exposed to it.

Then there are the POHs that expressly warn against using carb heat unless the pilot suspects the presence of carb ice...

Screenshot_20200307-140524_Adobe Acrobat.jpg
 
I recall as a general rule, carbureted Lycomings are less susceptible to carb ice than carbureted Continentals, due the Lycoming’s placement if the carb on the oil pan, which keeps it warmer and therefore less prone to ice.
 
I recall as a general rule, carbureted Lycomings are less susceptible to carb ice than carbureted Continentals, due the Lycoming’s placement if the carb on the oil pan, which keeps it warmer and therefore less prone to ice.
Depends on the airframe it's installed in, too. A Lycoming O-360-A4M in a Cherokee is rather ice-resistant, but in a C-172 like mine, it'll ice up without much provocation.
 
Carb ice is one of those things that once you’re on the ground smoking hole or not, therE is proof. Many of decent in the late summer I have had my carbureted continental 470 when I chop the power just a bit descending I hear the engine make just the slightest miss... I guess right perhaps and place the carb head on and
It might get better.... versus have the carb heat on on a warm summers eve and do a long procedure turn and turn to final and pier is low and heat is on and I hear that ‘Miss’ just A blimp really. .. I’m I to rich and not need the heat.- perhaps. But id rather that vs icing up.
 
That is so un-intuitive! I'm not a glider pilot, so maybe someone can help me with my thought experiment:

The Jolly Green Giant is standing in a field of beans with two identical model airplanes, one in each hand. Each has the same design, down to the last rivet, and are of the exact same size. Upon launch, which will glide farther, the one made from balsa and covered with tissue paper, or the one made from cast iron and covered with steel plate?​
It's a bit less extreme, but the Schweizer 1-26 is a good example of this:

The Schweizer 1-26 and 1-26A were fabric covered with a nominal empty weight of 338 pounds and a 550 pound gross weight. The wing area was 160 square feet giving in a wing loading of 3.59 lb/sq. ft. They had a L/D ratio of 23 to 1 at 48 mph and a minimum sink of 2.6 fps at 36 mph.

The design evolved through the B, C, D and E models with the final 1-26E being metal skinned (with the exception of the control surfaces) with a nominal empty weight of 455 pounds and a 700 pound gross weight. The wing area was the same 160 square feet giving in a higher wing loading of 4.38 lb/sq. ft. It had an identical L/D ratio of 23 to 1, but at 53 mph rather than 48 mph, and higher a minimum sink of 2.9 fps at a 4 mph faster 40 mph.

It's a single class sailplane and over the years the various models with steadily increasing weight and steadily increasing best glide and minimum sink speeds have generally all been equally competitive over time. But it is important to note that they are at their best in slightly different conditions.

The lighter 1-26, A, B and C versions do a bit better overall on days with weak lift due to the lower minimum sink, while the heavier D and E models do a bit better overall on days with stronger lift due to the greater best glide speed and better penetration.

Whether throwing out the DPE will stretch the glide or not, will depend on whether you've got a headwind or not. On a calm day throwing him out might help, but he'll frown on the technique.
 
And why would that be disqualifying? Unless you had to use the engine to make the spot, all else is available with perhaps the exception of pushing the examiner out the door to stretch the glide.

My understanding is that adding flaps and then taking them back off can be interpreted as failing this required skill:

"CA.IX.G.S6 - Maintain the manufacturer’s recommended approach airspeed ±5 knots in the landing configuration with a stabilized approach, until landing is assured."

I.e., if you add flaps and then put yourself in a position of coming up short, and having to reduce the flaps setting to reduce drag and extend the glide, you failed to properly maintain a stabilized approach.
 
Whether throwing out the DPE will stretch the glide or not, will depend on whether you've got a headwind or not. On a calm day throwing him out might help, but he'll frown on the technique.
Ouch (former DPE here).

On with my thought experiment, since @FastEddieB only restated the assertion and didn't help my intuitive grasp:

If L=W (approx), then L/D can be restated as W/D, right? And where W is constant, then best W/D occurs where D is least, right again? And since D decreases with weight (induced drag curve shifts leftward on total drag chart), whether the glide range stays the same would depend on whether the percentage of weight change is the same as the percentage of drag change. Right? Right?? So, what are the odds of that, huh? Color me skeptical.​
 
L/D is independent of speed, since it's Cl/Cd. Cl/Cd is at a maximum at a particular AOA regardless of airspeed. At any constant AOA both lift and drag vary with the square of airspeed. So best glide speed at any weight is the airspeed at which L=W at that particular AOA / Cl. The glide angle is the same, you're just flying along that angle faster or slower.
 
Dana has it.

Covered here as well:https://www.askacfi.com/1759/effect-of-weight-on-glide-ratio.htm

The answer from a link contained therein:

Variations in aircraft weight do not affect the glide angle provided that the correct airspeed is flown. Since it is the lift over drag (L/D) ratio that determines the gliding range, weight will not affect it. The glide ratio is based only on the relationship of the aerodynamic forces acting on the aircraft. The only effect weight has is to vary the time the aircraft will glide for. The heavier the aircraft is, the higher the airspeed must be to obtain the same glide ratio. If two aircraft have the same L/D ratio but different weights and start a glide from the same altitude, the heavier aircraft gliding at a higher airspeed will arrive at the same touchdown point in a shorter time. Both aircraft will cover the same distance but the lighter one will take a longer time to do so.
 
That’s a load of doo. The reason all the pilots I know who use carb heat push it off on final is to provide better power and throttle response for a go-around. I could tell two stories to illustrate that where carb heat on almost led to disastrous results. The standard procedure among pilots flying short strips is carb heat on for the approach and off on short final. That technique has withstood many a BFR.
There's a difference between the O-200 in a 150 and the O-470 in a 180, say. The 180's carb heat is over-the-top powerful and could cause some rough running if not taken off when the throttle is reopened. The habit a 150 pilot might get into in turning carb heat off shortly after turning final is just asking for trouble. It's not a big deal to push the carb heat in as the throttle is opened. And a 150, in cold weather, among other airplanes and engines, does respond better if the heat is still on until after the throttle is opened. It helps vaporize the accelerator pump fuel in the cold air.
 
Nope. Works the same. I have a little 150 time, too. Carb heat robs power. If your go-around doesn't require a high rate of climb it may not matter.
 
My understanding is that adding flaps and then taking them back off can be interpreted as failing this required skill:

"CA.IX.G.S6 - Maintain the manufacturer’s recommended approach airspeed ±5 knots in the landing configuration with a stabilized approach, until landing is assured."

I.e., if you add flaps and then put yourself in a position of coming up short, and having to reduce the flaps setting to reduce drag and extend the glide, you failed to properly maintain a stabilized approach.

You quoted the ACS section pertaining to multi-engine operations with an inoperative engine. For the commercial single engine power off 180, the pilot must correctly configure the aircraft to touch down at a specified point or up to 200 beyond. If full flaps and a stabilized approach ends up short, the task is failed. If the candidate has to suck up some flaps in order to hit the spot, that is the proper aircraft configuration to meet the task criteria to pass. The candidate does have to have knowledge of what constitutes a stabilized approach, but this particular task does not require a stabilized approach.
 
That’s a load of doo. The reason all the pilots I know who use carb heat push it off on final is to provide better power and throttle response for a go-around. I could tell two stories to illustrate that where carb heat on almost led to disastrous results. The standard procedure among pilots flying short strips is carb heat on for the approach and off on short final. That technique has withstood many a BFR.
There are many more stories where not using the carb heat led to disastrous results. You should know long before you are in a tight spot whether you would need to go around. In a 150 turning 2500rpm on climb out carb heat doesn’t make that much of a difference, maybe 100 fpm if that. Fear of poor airmanship is no excuse to not follow the POH and risk having no engine at all if you need it.
 
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