Flying above Service Ceiling?

[skidoo]

Is there any legal restriction from flying above your certified service ceiling if you are actually able to? For example, turbo 182 has a certified service ceiling of 20K ft, but its climb performance is still rated for 725 fpm at 20K. So, it looks capable of higher. So, I am wondering that if I am IFR and about to cross some ice laden clouds where their tops are at FL 200, could I legally request say 21 to 23K if the plane will actually take me there?

 

[Jim Logajan]

Nothing in Part 91 that I'm aware of. Perhaps there is a Part 121 or Part 135 issue?

 

[dmspilot]

Is there any legal restriction from flying above your certified service ceiling if you are actually able to? For example, turbo 182 has a certified service ceiling of 20K ft, but its climb performance is still rated for 725 fpm at 20K. So, it looks capable of higher. So, I am wondering that if I am IFR and about to cross some ice laden clouds where their tops are at FL 200, could I legally request say 21 to 23K if the plane will actually take me there?

The definition of service ceiling is the altitude at which climb rate reaches 100fpm. The 20,000' number is the Turbo 182's maximum operating altitude, not its service ceiling; and as the name implies, you may not operate above it.

 

[skidoo]

The definition of service ceiling is the altitude at which climb rate reaches 100fpm. The 20,000' number is the Turbo 182's maximum operating altitude, not its service ceiling; and as the name implies, you may not operate above it.

Thanks, I missed that...

 

[mrdavedpg]

I've always wondered this too, but more from the aerodynamic perspective.

So correct me if I'm wrong here please.

Once reaching the service ceiling the plane will continue to climb ~ 100fpm. Eventually I'm assuming it'll stop climbing. At this point it will just cruise along straight and level no? It will just require full power to do so. Does anything else interesting happen aerodynamically? Does the airplane handle any differently? Perhaps the controls become mushy or something?

Is the service ceiling determined by how much air the prop/engine combo can push over the wing? (though I suppose the shape of the wing would have some say in it as well, but assuming your basic single engine GA plane). I'm just guessing that a 172 pushes less air over it's wing than a turbo 182 and thus has a lower service ceiling.

 

[\__[Ô]__/]

The definition of service ceiling is the altitude at which climb rate reaches 100fpm. The 20,000' number is the Turbo 182's maximum operating altitude, not its service ceiling; and as the name implies, you may not operate above it.

I looked up the reg for max. operating altitude (see below). Is this a certification limit or a design limit? In other words, I know the rule applies to certification, but can I legally fly above the max. operating altitude? If not, is it the reg below that I'd be violating, or is there another one?


§23.1527 Maximum operating altitude.

(a) The maximum altitude up to which operation is allowed, as limited by flight, structural, powerplant, functional or equipment characteristics, must be established.

(b) A maximum operating altitude limitation of not more than 25,000 feet must be established for pressurized airplanes unless compliance with §23.775(e) is shown.

 

[midlifeflyer]

The reg violated would be 91.9(a).

And the limitation would also be identified in the "Limitations" section of a POH.

 

[FastEddieB]

The reg violated would be 91.9(a).

And the limitation would also be identified in the "Limitations" section of a POH.

So far as I know, recently certified planes will have a "maximum authorized altitude", in lieu of a service ceiling.

That's contained in Operating Limitations, so is limiting.

In a normally aspirated Cirrus SR22, it's 17,500', though the plane can certainly still climb well at that altitude.

 

[rottydaddy]

I've always wondered this too, but more from the aerodynamic perspective.

So correct me if I'm wrong here please.

Once reaching the service ceiling the plane will continue to climb ~ 100fpm. Eventually I'm assuming it'll stop climbing. At this point it will just cruise along straight and level no? It will just require full power to do so. Does anything else interesting happen aerodynamically? Does the airplane handle any differently? Perhaps the controls become mushy or something?

Is the service ceiling determined by how much air the prop/engine combo can push over the wing? (though I suppose the shape of the wing would have some say in it as well, but assuming your basic single engine GA plane). I'm just guessing that a 172 pushes less air over it's wing than a turbo 182 and thus has a lower service ceiling.

Airplanes don't fly because the prop pushes air over the wing. If that were the case, every "pusher" out there would be ground-bound, wouldn't it?

The prop pulls (or pushes) the airplane forward, and as the wing moves forward, it produces lift.

Obviously, in thinner air, the wing and the control surfaces will become less effective, but climb performance at high altitude is really all about available oxygen for the engine to use to burn the fuel being fed into it, and the pressure of the fuel/air mix. Every engine has a limit, even turbo or supercharged engines. Typically, the engine will reach its limit before the wing does. Service ceiling refers to that altitude at which the engine can only produce enough horsepower to sustain a climb at 100 fpm.

 

[alfadog]

Obviously, in thinner air, the wing and the control surfaces will become less effective, but climb performance at high altitude is really all about available oxygen for the engine to use to burn the fuel being fed into it, and the pressure of the fuel/air mix. Every engine has a limit, even turbo or supercharged engines. Typically, the engine will reach its limit before the wing does. Service ceiling refers to that altitude at which the engine can only produce enough horsepower to sustain a climb at 100 fpm.

Don't know why you would say that the wing is less effective at altitude. I would think that that the wing knows only its airspeed and is as effective at a given airspeed regardless of altitude.

Re the engine, my understanding is that climb performance is a function of surplus horsepower, i.e. how much hp the engine is capable of making in excess of that required to overcome drag at a given airspeed. An NA engine makes less horsepower at altitude because of the reduced density of the fuel-air charge and will reach a point where full throttle provides insufficient excess hp to climb.

 

[poadeleted20]

A "service ceiling" is strictly a performance number, not a limitation, and if you can get the plane to go higher, there's no reg violated (just mind the rule on supplemental O2 requirements). A "maximum authorized/operating altitude" in Section 2 Limitations of the POH is a legal limitation per 91.9, and cannot be legally exceeded.

 

[Capt. Geoffrey Thorpe]

Don't know why you would say that the wing is less effective at altitude. I would think that that the wing knows only its airspeed and is as effective at a given airspeed regardless of altitude.
.

L = (1/2) d v2 s CL

• L = Lift, which must equal the airplane's weight in pounds
• d = density of the air. This will change due to altitude. These values can be found in a I.C.A.O. Standard Atmosphere Table.
• v = velocity of an aircraft expressed in feet per second
• s = the wing area of an aircraft in square feet
• CL = Coefficient of lift , which is determined by the type of airfoil and angle of attack.

 

[Jaybird180]

A "service ceiling" is strictly a performance number, not a limitation, and if you can get the plane to go higher, there's no reg violated (just mind the rule on supplemental O2 requirements). A "maximum authorized/operating altitude" in Section 2 Limitations of the POH is a legal limitation per 91.9, and cannot be legally exceeded.

What is the relationship of 91.9 in this context to 91.3 (a)? Which is superior?

 

[poadeleted20]

What is the relationship of 91.9 in this context to 91.3 (a)?

I don't see what 91.3(a) has to do with this question.

Which is superior?

I don't see any conflict between those two regulations, so I see no issue of which is "superior".

 

[Jaybird180]

I don't see what 91.3(a) has to do with this question.
I don't see any conflict between those two regulations, so I see no issue of which is "superior".

91.3(a) says the PIC is the final authority as to the operation of the aircraft. In this case the limitations section says not to operate above xxx altitude and the PIC says that the aircraft continues to perform normally at xxx + yyy altitude.

 

[Clark1961]

91.3(a) says the PIC is the final authority as to the operation of the aircraft. In this case the limitations section says not to operate above xxx altitude and the PIC says that the aircraft continues to perform normally at xxx + yyy altitude.

Good luck with that. If it is a POH section two limitation chances are the altimeter check and transponder cert stop at that altitude. I know they do on the 'kota.

 

[Immelman]

Don't exceed the limitations of your airplane....

A corollary here is crosswind. Most airplanes have a maximum "demonstrated" crosswind; this is not a limitation. You can exceed it if you think its safe. Some aircraft have a limitation on maximum crosswind; don't exceed it.

Know your POH, AFM, and type certificate data sheet.

 

[alfadog]

L = (1/2) d v2 s CL

• L = Lift, which must equal the airplane's weight in pounds
• d = density of the air. This will change due to altitude. These values can be found in a I.C.A.O. Standard Atmosphere Table.
• v = velocity of an aircraft expressed in feet per second
• s = the wing area of an aircraft in square feet
• CL = Coefficient of lift , which is determined by the type of airfoil and angle of attack.

Sorry, I should have made myself clearer. When I said the wing knows only airspeed, I meant indicated airspeed (more correctly, equivalent airspeed). The velocity in that formula is true airspeed. When you convert true airspeed to indicated (equivalent) in that formula, the density cancels out. The wing is equally effective at a given indicated airspeed regardless of altitude.

Edit: Once you make the substitution, the formula becomes:

L=1/2*(rho sub 0)*(IAS)^2*s*CL

1. rho sub 0 is standard sea level density and is a constant
2. Assuming EAS = IAS, true for GA airspeeds and zero indicator error.

 

[alfadog]

A "service ceiling" is strictly a performance number, not a limitation, and if you can get the plane to go higher, there's no reg violated (just mind the rule on supplemental O2 requirements). A "maximum authorized/operating altitude" in Section 2 Limitations of the POH is a legal limitation per 91.9, and cannot be legally exceeded.

Why would they have that limitation of 20k? Could it be something as simple as the certification on the steam gauge instruments like the altimeter, etc.?

 

[poadeleted20]

91.3(a) says the PIC is the final authority as to the operation of the aircraft. In this case the limitations section says not to operate above xxx altitude and the PIC says that the aircraft continues to perform normally at xxx + yyy altitude.

All 91.3(a) means in this context is that the PIC eats the violation of 91.7 regardless of who's actually flying the plane. 91.3(a) most assuredly does not give pilots blanket authority to violate flight manual/type certificate limitations.

 

[skidoo]

All 91.3(a) means in this context is that the PIC eats the violation of 91.7 regardless of who's actually flying the plane. 91.3(a) most assuredly does not give pilots blanket authority to violate flight manual/type certificate limitations.

Consider this scenerio. Say I am flying at 20K, the max operating limitation for my aircraft. Obviously, I'm flying on an IFR clearance. I'm above the clouds, but ahead some cloud tops are at 20.5K. Because I'm at the operating limit, I continue and enter the clouds. After about 10 minutes, icing starts to form. If I request 21K will ATC allow that or otherwise Bust me if they do and I climb there. Or, would I need to declare an emergency to legally get there?

 

[FastEddieB]

Good luck with that. If it is a POH section two limitation chances are the altimeter check and transponder cert stop at that altitude. I know they do on the 'kota.

Furthermore at some altitude non-pressurized magnetos stop operating efficiently and will eventually malfunction.

Without knowing what that altitude is, well, we don't know what that altitude is.

All we know is that below the maximum authorized altitude they should be fine.

Above that, test pilot territory.

 

[skidoo]

Furthermore at some altitude non-pressurized magnetos stop operating efficiently and will eventually malfunction.

Without knowing what that altitude is, well, we don't know what that altitude is.

All we know is that below the maximum authorized altitude they should be fine.

Above that, test pilot territory.

Wouldn't that have to do with Density Altitude? Say one is at 20K actual but density altitude is 18K due to colder weather. On the other hand, say it was warmer weather and density altitude was 22K. Are you still OK to operate at 20K, or did the testing account for density altitude variations?

 

[Jaybird180]

All 91.3(a) means in this context is that the PIC eats the violation of 91.7 regardless of who's actually flying the plane. 91.3(a) most assuredly does not give pilots blanket authority to violate flight manual/type certificate limitations.

I agree with the latter part.

 

[kgruber]

Consider this scenerio. Say I am flying at 20K, the max operating limitation for my aircraft. Obviously, I'm flying on an IFR clearance. I'm above the clouds, but ahead some cloud tops are at 20.5K. Because I'm at the operating limit, I continue and enter the clouds. After about 10 minutes, icing starts to form. If I request 21K will ATC allow that or otherwise Bust me if they do and I climb there. Or, would I need to declare an emergency to legally get there?

No. ATC will not "bust" you. They don't know or care what your service ceiling is.

 

[alfadog]

Wouldn't that have to do with Density Altitude? Say one is at 20K actual but density altitude is 18K due to colder weather. On the other hand, say it was warmer weather and density altitude was 22K. Are you still OK to operate at 20K, or did the testing account for density altitude variations?

I imagine that 20k limit would be pressure altitude. There should be enough leeward in there to cover any non-standard condition issue.

 

[Jaybird180]

I think the key to all this is the term certification. It means that the aircraft as a whole has been tested and is known to function properly with the given set of circumstances. Afterwards, all bets are off.

If a limitation is given then operation outside of that means that some parameter required for certification will not behave as intended. It does not mean the craft will come hurtling out of the sky.

I've simulated max altitude before. I recommend you do the same. Interesting exercise on handling.

 

[Clark1961]

Furthermore at some altitude non-pressurized magnetos stop operating efficiently and will eventually malfunction.

Without knowing what that altitude is, well, we don't know what that altitude is.

All we know is that below the maximum authorized altitude they should be fine.

Above that, test pilot territory.

That's a good point on the mags and other components. As I understand it the mags could be damaged if operated at too high of altitude for too long.

I can add that the STC for pressurizing the mags did not raise the MOA for the 'kota. I did it anyway because of the potential for damage (arcing) and the STC was cheap in AMU terms while adding the intercooler and new fuel system.

All that said, there are unpressurized mags certified to operate at 25,000'. There may well be higher certified mags, I don't know.

 

[midlifeflyer]

91.3(a) says the PIC is the final authority as to the operation of the aircraft. In this case the limitations section says not to operate above xxx altitude and the PIC says that the aircraft continues to perform normally at xxx + yyy altitude.

The PIC is the final authority as to the operation of the aircraft within the FAR (absent an emergency).

Might as well ask whether 91.3(a) allows a VFR pilot to fly into the clouds if he simply chooses to as PIC.

 

[skidoo]

So, how would one actually get busted for exceeding the max operating altitude of the POH?

Would it make a difference if the pilot felt safer by doing so at the time?

 

[poadeleted20]

Consider this scenerio. Say I am flying at 20K, the max operating limitation for my aircraft. Obviously, I'm flying on an IFR clearance. I'm above the clouds, but ahead some cloud tops are at 20.5K. Because I'm at the operating limit, I continue and enter the clouds. After about 10 minutes, icing starts to form. If I request 21K will ATC allow that or otherwise Bust me if they do and I climb there. Or, would I need to declare an emergency to legally get there?

There are a lot of legal options, so why not choose one of them? And why did you put yourself in that box in the first place?

Y'all want to play games trying to find ways to do illegal things and get away with it, just leave me out.

 

[Clark1961]

So, how would one actually get busted for exceeding the max operating altitude of the POH?

The same way a pilot gets busted for violating any of the seeming minutia regulations: the pilot screws up something else and just gets caught on the subsequent investigation. If you've ever been part of an investigation by a well trained person/organization they dig into all the details. Well, all the details until they need an engineering staff then they may drop the ball.

 

[Pilawt]

Why would they have that limitation of 20k? Could it be something as simple as the certification on the steam gauge instruments like the altimeter, etc.?

A Piper Turbo Arrow, for example, has a service ceiling well above 20,000'. But it has a published "Maximum Operating Altitude" of 20,000' in the Limitations section of the POH -- I believe because of engine cooling issues as high altitude (Turbo Arrows don't have cowl flaps), and lack of pressurized magnetos.

Exceeding service ceiling has no legal ramification. As Ron said, it's merely a performance parameter, like "maximum rate of climb" or "maximum cruising speed". By definition, at "service ceiling" (density altitude) your airplane should be able to keep climbing at 100 fpm at gross weight. If yours does better, congratulations.

Exceeding "Maximum Operating Altitude" (if there is one; many airplanes don't have one) is another matter. That's a published limitation, like Vne or maximum gross weight. That's a no-no.

 

[skidoo]

There are a lot of legal options, so why not choose one of them? And why did you put yourself in that box in the first place?

Y'all want to play games trying to find ways to do illegal things and get away with it, just leave me out.

Not trying to do anything illegal. But, my box is narrower than most. With MEA's at 13K in virtually any direction from home base, I just want to understand ALL possible options. Forecasts are not perfect, and I can't always get it right either. I just need to understand the risks, either technical for operating, or legal risks. If it becomes evident that safety is becoming at risk while in flight, perhaps that would trump the legal risk, if one had to choose.

 

[poadeleted20]

Not trying to do anything illegal. But, my box is narrower than most. With MEA's at 13K in virtually any direction from home base, I just want to understand ALL possible options. Forecasts are not perfect, and I can't always get it right either. I just need to understand the risks, either technical for operating, or legal risks. If it becomes evident that safety is becoming at risk while in flight, perhaps that would trump the legal risk, if one had to choose.

The situation you describe sounds like a self-made emergency, and that does not fly past the FAA if it comes to their attention, no matter what 91.3 says. They're just not going to buy an argument that you had no reasonable warning of icing conditions ahead and had no choice but to continue forward when faced with higher clouds full of ice ahead at that sort of altitude. That's an emergency of your own making, and that does not sit well with them.

 

[skidoo]

The situation you describe sounds like a self-made emergency, and that does not fly past the FAA if it comes to their attention, no matter what 91.3 says. They're just not going to buy an argument that you had no reasonable warning of icing conditions ahead and had no choice but to continue forward when faced with higher clouds full of ice ahead at that sort of altitude. That's an emergency of your own making, and that does not sit well with them.

So, say that there were no airmets for icing in the area, no pireps, and forecast for only light icing, with a low probability en-route only from 7K to 14K, and I experience unforecast icing at 20K, you are saying my top priority should be fear the FAA, maybe not say anything and hope the icing is short lived, rather than ask for higher, or turn around?

Or, are you saying I should never have entered a cloud in the first place at below freezing even though there is no icing forecast? Since it is common to be below freezing at our MEA's, is it common for non FIKI IFR flights to divert around all clouds?

 

[Clark1961]

So, say that there were no airmets for icing in the area, no pireps, and forecast for only light icing, with a low probability en-route only from 7K to 14K, and I experience unforecast icing at 20K, you are saying my top priority should be fear the FAA, maybe not say anything and hope the icing is short lived, rather than ask for higher, or turn around?

Or, are you saying I should never have entered a cloud in the first place at below freezing even though there is no icing forecast? Since it is common to be below freezing at our MEA's, is it common for non FIKI IFR flights to divert around all clouds?

Just a reminder that clouds can/will be glaciated when more than 10 degrees (maybe more) below freezing. It's not as simple as saying we're below freezing...

 

[poadeleted20]

So, say that there were no airmets for icing in the area, no pireps, and forecast for only light icing, with a low probability en-route only from 7K to 14K, and I experience unforecast icing at 20K, you are saying my top priority should be fear the FAA, maybe not say anything and hope the icing is short lived, rather than ask for higher, or turn around?

I'm saying you're inventing highly improbable conditions in an effort to find a way to sneak past the rules, and I will not play that game with you.

 

[poadeleted20]

Just a reminder that clouds can/will be glaciated when more than 10 degrees (maybe more) below freezing. It's not as simple as saying we're below freezing...

10 below freezing (either F or C) is not a magic number below which icing cannot form. There's a lot more to the problem than just temperature. In fact, icing has been documented in temperatures as low as -40C.

 

[Everskyward]

So, say that there were no airmets for icing in the area, no pireps, and forecast for only light icing, with a low probability en-route only from 7K to 14K, and I experience unforecast icing at 20K, you are saying my top priority should be fear the FAA, maybe not say anything and hope the icing is short lived, rather than ask for higher, or turn around?

Or, are you saying I should never have entered a cloud in the first place at below freezing even though there is no icing forecast? Since it is common to be below freezing at our MEA's, is it common for non FIKI IFR flights to divert around all clouds?

Is your question really, "Will I get caught if I bust this limitation?"

Planning to climb out of the ice at 20,000' in a 182 is not such a good idea either since your climb rate will already be marginal even if it is not the true service ceiling, and icing is generally worse right in the tops.