How does flaps range and partial flaps work?

[kgruber]

Yep, that was one of the funny things in the O-470 powered Stinson. "Minimum Controlable Airspeed" had the ASI at 0. That was a fun plane.

Thank you, Phil Fields......who STC'd the first.

 

[Dan Thomas]

True that. It may "fly just fine" on one calm trip, but how much runway will it need on a warm day? What will be the stall characteristics? Or spin? Or how close will you be to structural failure in severe turbulence?

You ... don't ... know.

Add to that the fact that any older airplane that hasn't had an actual weight and balance done for a long time is most likely going to be heavier than all those W&B amendments would indicate. We regularly find airplanes 30 pounds heavier than the exisiting paperwork says they do. Paint, mods, dirt in the belly, repairs to the airframe: all of them add weight, and many times these things are done without any amendments at all. Or there are mistakes in the amendments.

I found a Citabria that was nearly 100 pounds heavier than the W&B paperwork said it was.

Dan

 

[bobmrg]

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?

No. Ask your instructor to show you where it says in black and white that what he is teaching is correct. Instructors are not perfect, and many are carriers of the Old Wive's Tale disease. Those of us who hang around the forums have read many stupid instructor tricks.

Bob Gardner

 

[Henning]

Thank you, Phil Fields......who STC'd the first.

It's an awesome climbing plane with that engine.

 

[asechrest]

I'll try to offer a different thought to the OP:

You seem to be analytic and methodical. Use that to your advantage, but remember that flying requires a large dose of "feeling" the airplane if you're doing it right. The air is a dynamic place, and while rigid adherence to procedure facilitates early learning, you've got to expand beyond that at some point in order to respond to everything that's thrown your way. It can become a hindrance if you can't ever get beyond the rote procedure you learned in your first handful of hours. Find your happy medium. Leverage your methodical approach where it makes sense, while remembering to keep a broad view of what it is you're doing up there so that when conditions call for it, you can adjust your procedure.

However, gross weight and flap speed limitations should always remain inflexible. Find a new instructor.

 

[kkoran]

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...

You don't have to tell him anything; just find another instructor.

 

[Gucci Pilot]

If you need flaps to slow down in a C-172....You are doing something wrong.

 

[woodchucker]

No. Ask your instructor to show you where it says in black and white that what he is teaching is correct. Instructors are not perfect, and many are carriers of the Old Wive's Tale disease. Those of us who hang around the forums have read many stupid instructor tricks.

Bob Gardner

Noted. I guess I felt I had good and consistent instructors, and their methodologies were consistent with the aircraft POH. But you are right, there are bad instructors (in all fields), and one needs to look out for that. Students can be vulnerable though, especially in an early learning stage. Students will listen to their instructors. A student won't have the time nor the energy to argue with an instructor in flight. If they say pull first notch now, unless there is some concern like the plane is in a steep dive and in the red arc, I would pull the first notch. If there is a problem with a cfi giving bad advice, then they need to be culled.

That said, I'm not sure I buy what is going on here. What CFI would say that being over gross is okay? Secondly, the OP states that they were over gross in a 150. Is that possible? On a training mission there won't be any baggage, and unless they are both 300+ pounds, is it possible to be over gross in a 150?

To put it kindly, my troll whiskers are twitching.

 

[woodchucker]

If you need flaps to slow down in a C-172....You are doing something wrong.

Or something is wrong. For example, the AWOS may not be correct. On my first XC solo I couldn't get the plane to 90 kts on the downwind. Re-checked AWOS and the winds had flipped.

 

[jesse]

Or something is wrong. For example, the AWOS may not be correct. On my first XC solo I couldn't get the plane to 90 kts on the downwind. Re-checked AWOS and the winds had flipped.

The wind would have nothing to do with slowing the airplane down regardless of which direction it was blowing.

 

[woodchucker]

The wind would have nothing to do with slowing the airplane down regardless of which direction it was blowing.

Sorry, let me clarify. The normal throttle setting wasn't yielding the normal IAS. Having to back way off on the throttle to achieve the pattern speed is what I was trying to convey.

Students need to learn to fly by the numbers, but they also need to gain an understanding of what the plane is telling them. A good cfi works on both aspects.

 

[rookie1255]

Just for clarification. When I did my primary training in a 150, it was not hard to approach gross, especially since I was pretty anal about flying with full fuel. I weigh 200lbs and I think my instructor weighed about the same if not a little more. This was always with no baggage.

Also, the flaps slowing down technique was never taught to me in a 172. When I transitioned to a 1966 Mooney M20E I always had trouble losing altitude and slowing down both getting to pattern altitude and landing. The technique worked, but in retrospect if I had known that it puts additional wear on flaps I wouldn't have done it. Luckily, airplane is sold now before I had any maintenance on flaps come up. If only I could have said the same for fuel tank leaks...

As far as flying over gross, one of the posts here made me think of something. Since a lot of GA aircraft often don't have real weight and balances done often, or many aren't even accurate, who's to say we don't have a bunch of people unknowingly flying as test pilots on a daily basis. I think people who actually use their airplanes probably load them up pretty close to gross, especially if taking full passenger/fuel load. Old/inaccurate weight and balances could make it easy to be outside "safe" limits.

Also, I don't know if there actually have been a significant number of accidents related to flying over gross. The more significant issue would be flying outside of CG. As far as being actually too heavy to fly, makes me wonder if there's a huge margin there I don't know about. Perhaps an aerospace engineer can chime in?

Maybe I am trolling though, call it a way to satisfy my curiosity about all things aviation and tapping into knowledge and experience that will hopefully fill in the gaps between all the "book learning."

 

[woodchucker]

Just for clarification. When I did my primary training in a 150, it was not hard to approach gross, especially since I was pretty anal about flying with full fuel. I weigh 200lbs and I think my instructor weighed about the same if not a little more.

Also, the flaps slowing down technique was never taught to me in a 172. When I transitioned to a 1966 Mooney M20E I always had trouble losing altitude and slowing down both getting to pattern altitude and landing. The technique worked, but in retrospect if I had known that it puts additional wear on flaps I wouldn't have done it. Luckily, airplane is sold now before I had any maintenance on flaps come up. If only I could have said the same for fuel tank leaks...

I apologize, I have never flown in a 150, and after a quick search it seems that 400 pounds left/right seats is pushing it. As PIC, it is okay to leave fuel behind though. So long as you have worked out the flight plan including reserves. Better to leave fuel behind than take off over gross, IMHO.

You don't really "slow down" the 172 with flaps. Just use throttle and pitch for that. But for landing, you do use 1st abeam, 2nd turning base, 3rd turning final. This optimizes the approach, and gets you at 65 kts final if the plane is at gross weight. You can easily use 60 kts if only two people and no baggage.

 

[flyingron]

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.

And add to that that SPEED is not what causes the stall. The Vso is only the point of stall in very specific conditions. You can stall faster or slower.

 

[FastEddieB]

Sorry, let me clarify. The normal throttle setting wasn't yielding the normal IAS. Having to back way off on the throttle to achieve the pattern speed is what I was trying to convey.

But, again, straight line winds cannot be a factor here.

You understand that, right?

 

[MAKG1]

And add to that that SPEED is not what causes the stall. The Vso is only the point of stall in very specific conditions. You can stall faster or slower.

If you are flying in a straight line at constant speed, the speed works just fine. It may not be the "cause" but it's predictable and measurable in almost every aircraft.

 

[MAKG1]

The wind would have nothing to do with slowing the airplane down regardless of which direction it was blowing.

Unless it's blowing up.

 

[PPC1052]

The certification regs now (and have always) required the top of the white arc to be Vfe.

​

​

I cannot say whether what you say is true. What I can say is that my POH for my 1976 Cessna 177B says that Vfe is 115 KIAS to 10 degrees, and the top of the white arc is 90 KIAS.

 

[bullwinkle]

[/INDENT]I cannot say whether what you say is true. What I can say is that my POH for my 1976 Cessna 177B says that Vfe is 115 KIAS to 10 degrees, and the top of the white arc is 90 KIAS.

Is the ASI in the airplane the original one? It is a thirty year old airplane.

 

[Henning]

Secondly, the OP states that they were over gross in a 150. Is that possible? On a training mission there won't be any baggage, and unless they are both 300+ pounds, is it possible to be over gross in a 150?

To put it kindly, my troll whiskers are twitching.

Have you ever worked weight and balance on a C-150? It's very easy to get over gross with 2 people and full fuel. The basic useful load is 510lbs or so and it holds 135 lbs of fuel leaving 375 for payload; that's 2, 187lb people.

 

[PPC1052]

Is the ASI in the airplane the original one? It is a thirty year old airplane.

Yes, it is the same airspeed indicator. Also, the same page of the POH that says that Vfe to 10 degrees is 115 KIAS also says that the top of the white arc is 90 KIAS. I am reading that page as I write this.

 

[bullwinkle]

Yes, it is the same airspeed indicator. Also, the same page of the POH that says that Vfe to 10 degrees is 115 KIAS also says that the top of the white arc is 90 KIAS. I am reading that page as I write this.

Cool.

 

[PPC1052]

Here is an image of the relevant page

 

[dans2992]

Just for clarification. When I did my primary training in a 150, it was not hard to approach gross, especially since I was pretty anal about flying with full fuel. I weigh 200lbs and I think my instructor weighed about the same if not a little more. This was always with no baggage.

Also, the flaps slowing down technique was never taught to me in a 172. When I transitioned to a 1966 Mooney M20E I always had trouble losing altitude and slowing down both getting to pattern altitude and landing. The technique worked, but in retrospect if I had known that it puts additional wear on flaps I wouldn't have done it. Luckily, airplane is sold now before I had any maintenance on flaps come up. If only I could have said the same for fuel tank leaks...

As far as flying over gross, one of the posts here made me think of something. Since a lot of GA aircraft often don't have real weight and balances done often, or many aren't even accurate, who's to say we don't have a bunch of people unknowingly flying as test pilots on a daily basis. I think people who actually use their airplanes probably load them up pretty close to gross, especially if taking full passenger/fuel load. Old/inaccurate weight and balances could make it easy to be outside "safe" limits.

Also, I don't know if there actually have been a significant number of accidents related to flying over gross. The more significant issue would be flying outside of CG. As far as being actually too heavy to fly, makes me wonder if there's a huge margin there I don't know about. Perhaps an aerospace engineer can chime in?

Maybe I am trolling though, call it a way to satisfy my curiosity about all things aviation and tapping into knowledge and experience that will hopefully fill in the gaps between all the "book learning."

I dealt with a plane once where the mechanics had made an error on the WB calculation.... 15 years ago! For those 15 years, if you loaded the plane to what you thought was max gross, you'd be 200 lbs over, and 2 inches beyond the aft limit! It was flown at "max gross" many times during those 15 years.


Sent from my iPad using Tapatalk

 

[exncsurfer]

I dealt with a plane once where the mechanics had made an error on the WB calculation.... 15 years ago! For those 15 years, if you loaded the plane to what you thought was max gross, you'd be 200 lbs over, and 2 inches beyond the aft limit! It was flown at "max gross" many times during those 15 years.


Sent from my iPad using Tapatalk

Right, but isn't this different than knowingly exceeding? I think its much different. Perhaps the design buffer(if there is such a thing) kept this plane from failing, but if you exceeded the limit intentionally in that case by 200, then you're 400 over.

Potentially incorrect WB is all the more reason not to exceed I think.

 

[kgruber]

Most aircraft came out of the factory with the weight value incorrect.

 

[Stewartb]

I dealt with a plane once where the mechanics had made an error on the WB calculation.... 15 years ago! For those 15 years, if you loaded the plane to what you thought was max gross, you'd be 200 lbs over, and 2 inches beyond the aft limit! It was flown at "max gross" many times during those 15 years.


Sent from my iPad using Tapatalk

I guess a "real" pilot is likely to have a "real stupid" mechanic?

 

[SkyDog58]

I dealt with a plane once where the mechanics had made an error on the WB calculation.... 15 years ago! For those 15 years, if you loaded the plane to what you thought was max gross, you'd be 200 lbs over, and 2 inches beyond the aft limit! It was flown at "max gross" many times during those 15 years.


Sent from my iPad using Tapatalk

Was this on an actual weigh job or on a post mod calculation? What type of airplane was it?

 

[bullwinkle]

Here is an image of the relevant page

Ah, there's the answer. Flaps less than 10° can be used up to 115kt, flaps 10°-30° can be used at the white arc, 90kt.

I assume flaps less than 10° is a non-standard mode to use, so it's not part of the white arc, which is the "normal" flap operation range.

 

[SkyDog58]

Ah, there's the answer. Flaps less than 10° can be used up to 115kt, flaps 10°-30° can be used at the white arc, 90kt.

I assume flaps less than 10° is a non-standard mode to use, so it's not part of the white arc, which is the "normal" flap operation range.

It is flaps to 10°, not less than 10°. It includes 10° and is not non-standard.

 

[MAKG1]

Ah, there's the answer. Flaps less than 10° can be used up to 115kt, flaps 10°-30° can be used at the white arc, 90kt.

I assume flaps less than 10° is a non-standard mode to use, so it's not part of the white arc, which is the "normal" flap operation range.

It's very common on Cessna singles.

It has nothing to do with "standard" modes. The white arc is the full flap operating range. The aircraft just has more than one Vfe specification.

You "can" use 10 flaps to help slow the aircraft, but as has been said before, it really isn't necessary on a draggy Cessna, especially if you have a CS prop at high RPM to pull to idle.

 

[Stewartb]

Also, I don't know if there actually have been a significant number of accidents related to flying over gross. The more significant issue would be flying outside of CG. As far as being actually too heavy to fly, makes me wonder if there's a huge margin there I don't know about. Perhaps an aerospace engineer can chime in?

A friend of mine was at the controls of his C-180 a few years ago when it crashed soon after takeoff. He had three of his kids and his mother in the plane along with weekend gear. A few other mutual friends witnessed the crash. We all surmised that the seat latch had broken. The NTSB confirmed that it had not. The final report centered on the overloading of the airplane. That's one example of an over gross contribution to five fatalities and sadly it hits a little too close to home. And on point with this thread, his airplane's loaded weight was under the max gross of my own 180. Two 180s but different airplanes. Weight matters.

Clearly you can horse an overloaded airplane into the air. The question is can you keep it there. Most experienced pilots will attest that a heavy airplane is easier to get off the ground in acceleration mode than to get safely back on the ground in deceleration mode. Be careful with the cavalier gross load attitude.

 

[bullwinkle]

It's very common on Cessna singles.

It has nothing to do with "standard" modes. The white arc is the full flap operating range. The aircraft just has more than one Vfe specification.

You "can" use 10 flaps to help slow the aircraft, but as has been said before, it really isn't necessary on a draggy Cessna, especially if you have a CS prop at high RPM to pull to idle.

Well...it's not entirely a full flaps range since the same operating range applies for both 30° (full flaps) and 11°-30° also.

The phrase "flaps to 10°" is ambiguous, and could mean "up to but not including" or "up to and including"...either interpretation is valid without clarification.

What are the flap settings available? If it's just 10, 20, and 30, then the POH probably means a setting of 10 is acceptable up to 115kt, but 20 and 30 require 90kt.

If the flaps are fully variable from 0-30, the conservative course would be to assume 115kt is reserved for 0-9 degrees and anything more the airplane should be at 90kt or below. Or just ask Cessna for clarification.

 

[MAKG1]

It gets even better.

All Cessna electric flaps are continuously variable, but they have discrete "notches" for legal takeoff positions. 172s and 177s have one at 10 deg, and 182s have two at 10 and 20 deg (182s are approved for takeoff at 20 deg for short and soft field takeoffs).

The white arc is not the operating range for flaps. It is the full flap operating range. It says as much in black and white in the POH. You can use the white arc to tell you when it is unambiguously safe to go to full flap, but you cannot use it to tell you anything about less than full flap. That's placarded on the flap switch if it isn't the same for all positions.

 

[Henning]

Regardless, any of these numbers are maximums, not minimums. The slower you are at any range of extension, the less wear and tear you induce. Learning to manage energy saves a lot of money in ownership.

 

[jesse]

Sorry, let me clarify. The normal throttle setting wasn't yielding the normal IAS. Having to back way off on the throttle to achieve the pattern speed is what I was trying to convey.

Students need to learn to fly by the numbers, but they also need to gain an understanding of what the plane is telling them. A good cfi works on both aspects.

The direction of the wind is not going to influence your airspeed. It will influence your ground speed. But it has nothing to do with a power setting not achieving an indicated airspeed. Something else was at play here, whether that was an instrument indication error, or the power setting for the airspeed wasn't what you remembered, or the setting wasn't set quite like you thought, you were in a bit of a descent and didn't realize it, or you simply didn't give it enough time to slow down.

 

[Clark1961]

That said, I'm not sure I buy what is going on here. What CFI would say that being over gross is okay? Secondly, the OP states that they were over gross in a 150. Is that possible? On a training mission there won't be any baggage, and unless they are both 300+ pounds, is it possible to be over gross in a 150?

To put it kindly, my troll whiskers are twitching.

Pretty easy to over weight in a 150 and I know at least one instructor that was willing to fly it overgross with a student. Dunno if he said it was okay but he certainly did it. My instructor, who owned the 150, called him out on it and made sure it didn't happen again.

 

[PPC1052]

I assume flaps less than 10° is a non-standard mode to use, so it's not part of the white arc, which is the "normal" flap operation range.

10 degrees is the first notch of flaps. I usually put them in abeam the numbers VFR (and at the FAF IFR), and I use one notch of flaps for take off as per the POH recommendation. So, less than 10, probably not standard, but 10 degrees is perfectly standard. I read the POH to say 10 degrees at 115 is okay.

 

[PPC1052]

It gets even better.

All Cessna electric flaps are continuously variable, but they have discrete "notches" for legal takeoff positions. 172s and 177s have one at 10 deg, and 182s have two at 10 and 20 deg (182s are approved for takeoff at 20 deg for short and soft field takeoffs).

In my 177B, there is a notch at 10, a notch at 20, and the bottom of the stop at 30, but yes, continuously variable between the notches.

One thing about the 177B flaps is that the beginning of their movement is straight back. After they go straight back, then then rotate down. Per Cardinal Flyers Online, the first 5 degrees only increases flap surface area and does not change the angle.

 

[woodchucker]

The direction of the wind is not going to influence your airspeed. It will influence your ground speed. But it has nothing to do with a power setting not achieving an indicated airspeed. Something else was at play here, whether that was an instrument indication error, or the power setting for the airspeed wasn't what you remembered, or the setting wasn't set quite like you thought, you were in a bit of a descent and didn't realize it, or you simply didn't give it enough time to slow down.

Jesse, my memory admittedly is a bit fuzzy on it. That was more than a year ago. It was my first solo XC so low hours accompanied by low experience. Thinking back, all I remember is that it didn't feel right. As I mentioned, things weren't happening with the timing between events that I normally expected (GS issue, not IAS). Confirming with AWOS, the winds were shifting about the compass. It took me a few circuits around before I felt comfortable in getting the wheels to the ground. That flight was a great learning experience.

Anyways, if your location is where your profile says it is, I pass through there every now and then. Maybe next summer. I would be happy to grab a lesson with you. I love learning.