How does flaps range and partial flaps work?

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rookie1255

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rookie1255
2 questions about flaps

1. So the upper end of the white arc is the maximum speed for full flaps, but my instructor has had me deploy partial flaps above that speed in order to slow down if needed. Basically to use partial flaps as speed brakes. How do I know what airspeed is ok to deploy what amount of flaps and not cause damage when it comes to partial flaps above white arc airspeeds?

2. Flaps increase lift and drag allowing the airplane to fly slower without reaching critical angle of attack and stalling. The bottom end of the white arc gives the minimum airspeed with full flaps. I was taught to deploy flaps in stages. Partial flaps on base, rest on final, etc... My question is how do I know the minimum airspeed I can fly with partial flaps? Partial flaps mean partial additional lift so I should not fly the bottom of the white arc airspeed with partial flaps. However, I also don't want to carry unnecessary additional airspeed since it'll just increase kinetic energy, make management more difficult, and potentially increase landing distance.
 
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rookie1255 said:
2 questions about flaps

1. So the upper end of the white arc is the maximum speed for full flaps, but my instructor has had me deploy partial flaps above that speed in order to slow down if needed. Basically to use partial flaps as speed brakes. How do I know what airspeed is ok to deploy what amount of flaps and not cause damage when it comes to partial flaps above white arc airspeeds?
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Deploying *ANY* flaps is not permitted above the flaps range unless the POH permits it. Check the POH. What year and model airplane are you flying?

2. Flaps increase lift at slower airspeeds allowing the airplane to fly without reaching critical angle of attack and stalling. The bottom end of the white arc gives the minimum airspeed with full flaps. I was taught to deploy flaps in stages. Partial flaps on base, rest on final, etc... My question is how do I know the minimum airspeed I can fly with partial flaps? Partial flaps mean partial additional lift so I should not fly the bottom of the white arc airspeed with partial flaps. However, I also don't want to carry unnecessary additional airspeed since it'll just increase kinetic energy and landing distance.
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Well for starters those are based on gross weight, so with less weight, the stall speed is going to be lower than indicated. That said, there are few airplanes where you'd be below the zero flaps stall speed at any point in the pattern so I'm not sure what you're worrying about.

At the end of the day you have to LEARN what the airplane FEELS like as it approaches a stall and that's the best you're going to get short of having an angle of attack indicator (which few GA airplanes have).

Don't overthink it. Just fly it.
 
I've done this procedure with flaps in a 172 and an 1966 Mooney M20E. Neither POH says it's ok, but my CFI has had me do it a couple of times in flight. When I asked him how to know it was ok to do so he gave the same response, "you'll figure it out with experience."

To me that seems really unscientific. I mean, what if I guess and I'm wrong? The traffic pattern would not be a good place to get into that kind of trouble.

Another potential safety concern I've had is flying over gross. I've done weight and balance and it used to be mostly an issue in the 150. With fuel we would be overweight and my CFI's response would be "don't worry, she'll fly." Well, I worried anyways, but he was right, we flew fine. So now that begs the question, since gross weight isn't really gross weight, what is the actual weight limit for an aircraft? At what point would she NOT fly? Is there a standard margin built into all aircraft and how far is it ok to go into that margin?

Maybe I AM overthinking it, my CFI says I am and now a CFI here has posted the same thing. I guess it would be nice to have some clarity and know where lines are so I know where to walk. I want to be safe, but I also don't want to be the dummy who won't take off cause I'm 5 pounds over gross while the real pilots on the ramp snicker and laugh at me.
 
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rookie1255 said:
I've done this procedure with flaps in a 172 and an 1966 Mooney M20E. Neither POH says it's ok, but my CFI has had me do it a couple of times in flight. When I asked him how to know it was ok to do so he gave the same response, "you'll figure it out with experience."

To me that seems really unscientific. I mean, what if I guess and I'm wrong? The traffic pattern would not be a good place to get into that kind of trouble.
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If the POH does not permit flaps being deployed above the max flap speed, which it doesn't, unless it specifically says something like 10 degrees flaps at X speed....then the answer is simple....do not deploy flaps above that speed and your CFI should not be teaching otherwise.

There simply is no reason to be adding flaps above the speed at which they were designed to be added in any airplane. If an instructor thinks one needs to do that they probably need to be whacked upside the head and learn some airmanship. Remove power, hold nose up so you don't descend, you slow down.

rookie1255 said:
Another potential safety concern I've had is flying over gross. I've done weight and balance and it used to be mostly an issue in the 150. With fuel we would be overweight and my CFI's response would be "don't worry, she fly." Well, I worried anyways, but he was right, we flew fine. So now that begs the question, since gross weight isn't really gross weight, what is the actual weight limit for an aircraft? At what point would she NOT fly? Is there a standard margin built into all aircraft and how far is it ok to go into that margin?

Maybe I AM overthinking it, my CFI says I am and now a CFI here has posted the same thing. I guess it would be nice to have some clarity and know where lines are so I know where to walk. I want to be safe, but I also don't want to be the dummy who won't take off cause I'm 5 pounds over gross while the real pilots on the ramp snicker and laugh at me.
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As a flight instructor I absolutely would never tell someone it is "OK" to fly over gross. Because it's not OK, it is illegal, and the FAA could take action against me for doing so.

Will it fly above gross? Yeah it will. How far above gross will it fly? Well...that depends. You're reaching beyond the certification standards and you have no performance data in the POH to support it.

What was the determining factor for the gross weight being what it is? Often times it has to do with go around criteria in the certification standards and is limited by lack of horsepower. Other times there may be plenty of horsepower and it's really a structural issue that caused the limit. Unless you can dig up the guys who designed the airframe there really is no way to know.

Regardless of if it is possible and how safe it isn't or isn't at the end of the day it is illegal. Teaching things that are illegal isn't how ethical instructors do business. Just my opinion, YMMV, blah blah :)

Why do something that's illegal and one can lose their flying or instructing privileges over by doing it? Doesn't make much sense to me..much easier to just operate legally. Standards are there for a reason.

I can absolutely assure you that a CFI would not pass a CFI checkride telling the inspector that it's OK to deploy flaps above max flap speed or that its OK to fly above max gross.

If what your CFI is telling you wouldn't fly under the eyes of the FAA..then that should tell you everything you need to know.
 
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Thanks for the replies Jesse. I know that I'll tend to be a more "by the books" kind of guy and your advice seems sound. At the same time, my CFI has over 15,000 hours, flew for airlines, and started flying before my dad was born. It would be weird telling him "well, this isn't safe," or "well, this is how you're SUPPOSED to fly." I guess that's more of an interpersonal issue than an aviation issue though...
 
rookie1255 said:
Thanks for the replies Jesse. I know that I'll tend to be a more "by the books" kind of guy and your advice seems sound. At the same time, my CFI has over 15,000 hours, flew for airlines, and started flying before my dad was born. It would be weird telling him "well, this isn't safe," or "well, this is how you're SUPPOSED to fly." I guess that's more of an interpersonal issue than an aviation issue though...
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I understand what you're saying...and yes there is margin built into many of these things. Yes you could probably put some flaps down X percentage over max flap speed and be OK. You could probably do that your entire life if you wanted.

But, why? If someone told me they wanted me to do that, and FAA issues aside, I would ask them to show me the engineering data behind their logic that it is OK to deploy flaps faster than the engineers said it was OK. I seriously doubt they know something the engineers didn't.

At the end of the day this is a decision you'll have to make for yourself. I can tell you that if a student told me an instructor in one of our aircraft taught them it was OK to deploy flaps above max flap speed and wanted them to do that instead of showing them how to properly slow the airplane down via other manners they wouldn't be teaching in our planes anymore.
 
Some 172 models allow for 10 degrees of flaps at 110 KIAS and then you have to be at or under 85 KIAS (white arc) for any setting greater than 10 degrees. This is normally indicated on the flap handle.


AF-flap-switch-feature.jpg
 
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Question 1: usually the speeds for the flap settings are printed next to the switch. They may or may not be in the POH. Otherwise, listen to your instructor's advice on what speed you can safely deploy the first notch of flaps.

Question 2: You probably learned something like 1st notch abeam the numbers, 2nd notch turning base, 3rd notch turning final. Speeds typically around 85ish, 75ish, 65ish depending on your plane. You are wise to be concerned about carrying too much energy into the landing. While on final, just focus on two things: the sight picture of the runway, and your airspeed. If you refer to your POH, follow the landing speed provided while on final.

I'm really not sure what you are worked up over with carrying too much energy. Follow the POH, and listen to your instructor.

You are flying real planes, right? With an instructor? Not learning how to fly on your own using MSFX or something like that?
 
rookie1255 said:
2 questions about flaps

2. Flaps increase lift and drag allowing the airplane to fly slower without reaching critical angle of attack and stalling. The bottom end of the white arc gives the minimum airspeed with full flaps. I was taught to deploy flaps in stages. Partial flaps on base, rest on final, etc... My question is how do I know the minimum airspeed I can fly with partial flaps? Partial flaps mean partial additional lift so I should not fly the bottom of the white arc airspeed with partial flaps. However, I also don't want to carry unnecessary additional airspeed since it'll just increase kinetic energy, make management more difficult, and potentially increase landing distance.
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You could be "safe" and simply not fly slower than the bottom of the green arc. Your approach speed can be calculated in many cases to be 1.3 times the relevant stall speed, pulling power and bleeding off excess speed in the flare. In draggy spam cans this isn't a problem. In slick, fast airframes, you need to be on target with your speed and energy management.

What speeds does your checklist and POH call out for approach and landing?
 
Regardless of the white arc, there is an established Vfe in the aircraft POH which denotes the maximum speed that any degree of flaps may be safely deployed. It's not an issue of slowing the airplane, but one of not overstressing and potentially damaging the flap mechanism. Using flaps to slow an airplane should not be employed as a routine technique to address bad planning. You CFI should focus instead on better airmanship. If you need to slow the plane, reduce the power and raise the nose and let the speed bleed off. If you're in the pattern and you still need to reduce the speed even further, extend your downwind a little. If you're in a hot-rod, then you should have speed brakes for this function.
 
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rookie1255 said:
Thanks for the replies Jesse. I know that I'll tend to be a more "by the books" kind of guy and your advice seems sound. At the same time, my CFI has over 15,000 hours, flew for airlines, and started flying before my dad was born. It would be weird telling him "well, this isn't safe," or "well, this is how you're SUPPOSED to fly." I guess that's more of an interpersonal issue than an aviation issue though...
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I wonder how many pilot candidates he has put up for a check ride, that deployed flaps above the POH speed, and busted the ride based on "but the instructor said it was ok".
 
SkyDog58 said:
Some 172 models allow for 10 degrees of flaps at 110 KIAS and then you have to be at or under 85 KIAS (white arc) for any setting greater than 10 degrees. This is normally indicated on the flap handle.


AF-flap-switch-feature.jpg
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There are a few aircraft that allow different flap settings at different speeds. It will be in the POH and printed next to the flap control. Older 172s do not have that capability.
 
If your reporting is accurate, I would find a new instructor.

Pilots should be taught from the first hour to respect a plane's limitations.

One should never touch a flap switch or handle without a glance at the airspeed indicator to confirm its in the white arc*.

Similarly, one should never initiate a flight over gross.**

If the instructor truly has you ignoring limitations from the get go, the Law of Primacy may set you up to ingrain such habits as "normal" - they are not.


*Allowing for published "partial flap" speeds.

**Except in isolated cases - ferry flight with proper precautions, etc.
 
As a mechanic and pilot, I don't even deploy flaps to 10 degrees at 115 even though its placarded for it. I'd much rather reduce power, trim up and slow to 80 before adding any. Overstressed flap tracks can crack the angles that attach them to the skins, the skins themselves, or even worse, crack wing spars at the rivet holes.
 
As an owner I respect Vfe and Vlo. You might get away with operating these devices above recommended speeds, but I'd wager they will wear and need MX at a faster rate if you do. Just like avoiding heavy brake use, fly smart and reduce your MX costs.
 
Taught to use flaps to slow down? Find a better instructor. Like one who knows how to fly.
 
Over speed on flaps over weight and bad landings A&P got to eat too. The big bucks $$$ are in fixing aircraft not teaching people to fly.:rofl:
 
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SbestCFII said:
Regardless of the white arc, there is an established Vfe in the aircraft POH which denotes the maximum speed that any degree of flaps may be safely deployed.
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The certification regs now (and have always) required the top of the white arc to be Vfe.

(4) For the flap operating range, a white arc with the lower limit at V S0 at the maximum weight, and the upper limit at the flaps-extended speed V FE established under § 23.1511.​

The flap speed is determined by structural limits based on the airspeed involved, 25% gusts, and the propeller slipstream effects.

The instructor (as stated) is full of crap. There is no level of experimentation or experience that can legally or practically modify these limits.
 
The way it was explained to me is that the upper limit of the flap arc is the maximum speed for deployment of full flaps. Therefore partial flaps would not cause over stress. Whether this is true or not I don't know.

As for flying over gross, I would be more apt to criticize my instructor if I didn't see old pilots do it all the time. For that I've heard that these airplanes are so old and have been modified so many times that if they stuck to book values the airplane would barely carry 2 people. This is especially the case in Mooneys with mods like long range tanks. I've also heard that the over gross isn't too much to worry about unless it's on a hot day or it's a short runway.

So far the answer seems to be to ignore what anyone says or what their experience is, and go by what the book gives as the answer. Seems right to me, but I am telling you, these people are not outliers, they are the norm. At least in my area they are (far upstate NY).
 
+1 For finding a new instructor, and quick like, is not fast enough...
My aircraft calls for Max. gear down speed of 150 m.p.h. and Max. flap deployment speed of 125 m.p.h.
Recommended speeds are 125 on the gear and 100 on the flaps to reduce wear and ease the air loads.
I fly using the recommended speeds.:yes:
I wouldn't be paying for an instructor that's telling me to do the opposite!!:no:
 
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The 110-KIAS "approach-flap" limit on the first 10 degrees of flap extension was added with the 1979 C-172N (s/n 17271035 and up). It was just a "paper" change; no structural or mechanical modification involved. Earlier C-172M and N models can also take advantage of the change under Air Plains STC SA2196CE.

That said, flap operation at higher speeds just adds stress and wear to the system. Better to plan ahead and drop flaps at lower speeds. An airline pilot friend of mine tells me his company strongly encourages its pilots to consider flap limit speed to be 10-20 KIAS below published Vfe.
 
Depends.

My Aerostar has no speed limit for 10 degree flap deployment. I can take that out right Vne if I want to. It has 174kts for Vf20 which is 20 degrees flap. I use both settings as a speed brake all the time. Still well above the white arc, which is FULL flap deployment. That comes around 148kts and is referred to as Vf. Never any mention of Vfe in the POH.

It's hard to slow down to gear extension speeds (156kts) without using the flaps on the A*. It's a very slippery airframe. And it's almost impossible to get to pattern speed without extending gear. This is good, because it makes a gear up landing less likely. Still - hasn't stopped a few from doing that anyhow...:D
 
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rookie1255 said:
2 questions about flaps

1. So the upper end of the white arc is the maximum speed for full flaps, but my instructor has had me deploy partial flaps above that speed in order to slow down if needed. Basically to use partial flaps as speed brakes. How do I know what airspeed is ok to deploy what amount of flaps and not cause damage when it comes to partial flaps above white arc airspeeds?

2. Flaps increase lift and drag allowing the airplane to fly slower without reaching critical angle of attack and stalling. The bottom end of the white arc gives the minimum airspeed with full flaps. I was taught to deploy flaps in stages. Partial flaps on base, rest on final, etc... My question is how do I know the minimum airspeed I can fly with partial flaps? Partial flaps mean partial additional lift so I should not fly the bottom of the white arc airspeed with partial flaps. However, I also don't want to carry unnecessary additional airspeed since it'll just increase kinetic energy, make management more difficult, and potentially increase landing distance.
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Eeesh, I don't even put the flaps out at the top of the white arc to save wear and tear on the loaded components. As for minimum speed, feel the yoke and listen for the stall horn, as it changes with weight. My last FR the instructor asked for a "short field landing". We were in a 172 with 300lbs in the cabin and quarter tanks. Coming down final the instructor points out, "We're below the white arc." "Yes, so? We're flying still right?" "Yes" "Stall horn isn't on" "nope" "Approach is stable heading right for the threshold right?" "Looks good" "Then what's the problem?" "None really". When we landed the tower called and said "We scored that one a 10.":D

Numbers matter, but you have to remember the published numbers for GA are for Max Gross. In GA aircraft it's easier to modify the numbers for reduced weight by the feel of the yoke than by calculating them. Airliners all have 'speed cards' that give the correct speeds at several weights, and many modern ones will "bug" the correct speed for current weight.
 
Different flap settings can have different speeds, but if only one Vfe speed is listed you have to assume that is for any setting except up. My airplane has several flap settings, some have different speed limits:

40° : 62kt

30° : 62kt

15° : 80kt

0° : 100kt

-6° : Vne (145kt)
 
If you're not trolling with this thread - sorry, but it happens - then you're getting some horrible advice from your instructor and you're finding horrible examples of poor airmanship around.

Accident reports where being over gross is listed as a contributing cause are depressingly common. I personally had a rental plane destroyed and saw two lives lost where flying over gross was a factor.

Please find an instructor that goes by the book. Most should.
 
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Something has been missed is that is IS possible to fly below the white arc with full flap. BTDT, in level slow flight, in several aircraft.

The white arc is for max gross weight. If you're well below max gross weight, all the stall speeds will be lower.
 
jesse said:
I understand what you're saying...and yes there is margin built into many of these things. Yes you could probably put some flaps down X percentage over max flap speed and be OK. You could probably do that your entire life if you wanted.

But, why? If someone told me they wanted me to do that, and FAA issues aside, I would ask them to show me the engineering data behind their logic that it is OK to deploy flaps faster than the engineers said it was OK. I seriously doubt they know something the engineers didn't.

At the end of the day this is a decision you'll have to make for yourself. I can tell you that if a student told me an instructor in one of our aircraft taught them it was OK to deploy flaps above max flap speed and wanted them to do that instead of showing them how to properly slow the airplane down via other manners they wouldn't be teaching in our planes anymore.
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Jesse is absolutely correct, regardless how many hours the instructor has and that he started flying when Christ was but a child. ( he's wrong)
 
MAKG1 said:
Something has been missed is that is IS possible to fly below the white arc with full flap. BTDT, in level slow flight, in several aircraft.

The white arc is for max gross weight. If you're well below max gross weight, all the stall speeds will be lower.
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Heck, you can fly at O knots indicated, too.
 
+1 to most of what's already been said.

Another thing to remember is that at the end of the day, you will be the pilot in command. That means the decision is yours, and the responsibility is yours, AND the authority is yours. "My instructor said" will be irrelevant.

If you don't feel comfortable doing something (and in the examples you cited, you absolutely shouldn't, in my opinion) you have every right to stand behind your decision not to do it. That can be hard when you're just learning and you're not sure what's right, but it's still true.

I wouldn't be surprised to see an examiner on a check ride ask you to do something you shouldn't (probably phrased as "can we" rather than "do this"), to check your judgment and willingness to be in command. Hasn't happened to me personally though.

If you generally like your current instructor, you could try insisting on doing things by the book even when he wants to be fast and loose about it and see how he responds. If he doesn't like it and wants to drop you, it's probably just as well. Of course, if he's fine with it the problem is that you may not know when you need a second opinion about other things he tells you.
 
deyoung said:
+1 to most of what's already been said.

Another thing to remember is that at the end of the day, you will be the pilot in command. That means the decision is yours, and the responsibility is yours, AND the authority is yours. "My instructor said" will be irrelevant.

If you don't feel comfortable doing something (and in the examples you cited, you absolutely shouldn't, in my opinion) you have every right to stand behind your decision not to do it. That can be hard when you're just learning and you're not sure what's right, but it's still true.

I wouldn't be surprised to see an examiner on a check ride ask you to do something you shouldn't (probably phrased as "can we" rather than "do this"), to check your judgment and willingness to be in command. Hasn't happened to me personally though.

If you generally like your current instructor, you could try insisting on doing things by the book even when he wants to be fast and loose about it and see how he responds. If he doesn't like it and wants to drop you, it's probably just as well. Of course, if he's fine with it the problem is that you may not know when you need a second opinion about other things he tells you.
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+1.

Part of your training is to get you to be PIC and to get you into that mindset. You need to make the decisions, you need to live with the consequences. If you tell your CFI, "Yeah, I KNOW it'll fly above max gross, but the book says max gross and the W&B calculations show greater than max gross, but I'm the one training to be PIC and I think we need to work this out", I wonder what kind of reaction you'll get?
 
Pilawt said:
An airline pilot friend of mine tells me his company strongly encourages its pilots to consider flap limit speed to be 10-20 KIAS below published Vfe.
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My airline is even more aggressive than that - suggesting that we slow to green dot + 10 before configuring further. Obviously that's not always possible, but I make the effort whenever I'm in a position to do so. Depending on weight, that speed can be a good 50 knots less than the upper limit.

I carry that thinking into my GA flying too. I'm still a renter (sigh...), but I have a personal policy to fly anything as though I own it myself.
 
A 172 is a draggy airplane. If one needs to slow down he should just pull the power back and raise the nose. He doesn't need to go sticking flaps out to slow down. I often see long, high, hot landings in light singles, mostly because the pilot is afraid to reduce the power, for some reason. Afraid of stalling or something? I'd be willing to bet that more airplanes are busted by landing too fast than by stalling on final. Bouncing, porpoising, wheelbarrowing, ballooning, skidding the tires and blowing them out, or running off the end of the runway are far more common than stalling on final.

Dan
 
Back to the OP. A Cessna flies great at pattern entry speed with no flaps. You'd be better served by entering the pattern at your target speed and deploy the first notch abeam your touchdown point on the runway. In my 180 I never pull the first notch until I'm at or below 90mph. Never. Base sees me decelerate to 80 before a second notch. I turn final at about 70, pull the third notch, and when comfy that I won't balk the landing I'll go 4th notch and decelerate to 65 or 60 for normal ops. I can't see any reason to ever deploy any flaps until 90 and then only if I'm planning to loiter and maneuver at slow speed or descend to land. Guys can argue the fine points all they want but every Cessna driver I know does it about the same as me. And I know some sh-t hot Cessna drivers. Learn to slow the plane in preparation to land rather than using flaps incorrectly in response to a poor approach. You'll be better for it.
 
rookie1255 said:
I've done this procedure with flaps in a 172 and an 1966 Mooney M20E. Neither POH says it's ok, but my CFI has had me do it a couple of times in flight. When I asked him how to know it was ok to do so he gave the same response, "you'll figure it out with experience."

To me that seems really unscientific. I mean, what if I guess and I'm wrong? The traffic pattern would not be a good place to get into that kind of trouble.

Another potential safety concern I've had is flying over gross. I've done weight and balance and it used to be mostly an issue in the 150. With fuel we would be overweight and my CFI's response would be "don't worry, she'll fly." Well, I worried anyways, but he was right, we flew fine. So now that begs the question, since gross weight isn't really gross weight, what is the actual weight limit for an aircraft? At what point would she NOT fly? Is there a standard margin built into all aircraft and how far is it ok to go into that margin?

Maybe I AM overthinking it, my CFI says I am and now a CFI here has posted the same thing. I guess it would be nice to have some clarity and know where lines are so I know where to walk. I want to be safe, but I also don't want to be the dummy who won't take off cause I'm 5 pounds over gross while the real pilots on the ramp snicker and laugh at me.
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Let the "real" pilots snicker. Gross weight is your maximum airworthy weight. Whether if flies or not is not your concern. That it performs to specs is your concern. At one pound over gross you're literally a test pilot. If you're worthy of that title you wouldn't be on this forum asking these questions, right?
 
I will offer a few things to consider. In my airplanes the performance reduction with added weight is fairly linear until you get to gross, and then the performance declines rapidly. At least that's my perception after 25 years of operating on the same smallish strip. To be fair my airplanes have had approved gross weight increases. What's the approach speed of an over-gross airplane? Hard to say other than it's faster than published speeds. What's the sink rate? Climb rate? How do the controls respond? Does the tail maintain authority when you get slow? How does the airframe react to a hard landing, which is inevitable until you answer the other questions? How do the brakes work? Most experienced pilots scare the crap out of themselves once or twice and then they become more conservative. No brag, no embellishment, just real.
 
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