up, down or back @ 17500 feet?

Guest Discussion
1

I had a nice trip from gjt>saa>shr>saa>gjt on saturday, but on the last leg of the trip i ran into a situation that got me thinking.

I was VFR @ 16500 on top of an aproximate 4000’ thick layer
i could see on the xm that the coverage was solid until just short of grandjunction. I was alone with no luggage and only 40 gal fuel. As i got about half way across the undercast i noticed that the top had risen to my level. I was able to cruise climb LOP at about 400 feet per minute with a IAS of 120kts up to 17500 easily clear the rest of the undercast and finish my trip.

FYI (@17500 i saw a TAS of 175 and a GS 205 At about 10.5 g/h
OAT was -17C)

But After i had landed i got to wondering what i would have done had the tops been 17500 or 18500.

I feel there would have been four choices:

1.Go IFR through the layer and try to get below it.
This seems like a no go as there are 12k mountains in the area and i could not be sure how low the ceilings where.

2.Go IFR through the clouds.
My plane does not have tks and it was below freezing all the way to the ground.

3.turn around
simple and safe but it does leave me in saratoga wy for the night.

4.Go IFR and climb the extra 1000’ feet to clear the tops.
This seems very possible but it exceeds the service ceiling of the plane. Is there a safty reason for the 17500 limit or is it just that cirrus didn’t want to do the extra paper work. I understand the power situation aka your not going to FL25 in a NA but i was there and there was plenty of power to go up to FL20.

Its probably not a situation thats going to come up a lot for most people but for us mountain dwellers there are times when it does.

I’ll be interested to see what you all think. Has anyone gone higher i have to think some people have judging from how ready the plane was to do it.

Blu

2

In reply to:

I had a nice trip from gjt>saa>shr>saa>gjt on saturday, but on the last leg of the trip i ran into a situation that got me thinking.
I was VFR @ 16500 on top of an aproximate 4000’ thick layer
i could see on the xm that the coverage was solid until just short of grandjunction. I was alone with no luggage and only 40 gal fuel. As i got about half way across the undercast i noticed that the top had risen to my level. I was able to cruise climb LOP at about 400 feet per minute with a IAS of 120kts up to 17500 easily clear the rest of the undercast and finish my trip.
FYI (@17500 i saw a TAS of 175 and a GS 205 At about 10.5 g/h
OAT was -17C)
But After i had landed i got to wondering what i would have done had the tops been 17500 or 18500.
I feel there would have been four choices:
1.Go IFR through the layer and try to get below it.
This seems like a no go as there are 12k mountains in the area and i could not be sure how low the ceilings where.
2.Go IFR through the clouds.
My plane does not have tks and it was below freezing all the way to the ground.
3.turn around
simple and safe but it does leave me in saratoga wy for the night.
4.Go IFR and climb the extra 1000’ feet to clear the tops.
This seems very possible but it exceeds the service ceiling of the plane. Is there a safty reason for the 17500 limit or is it just that cirrus didn’t want to do the extra paper work. I understand the power situation aka your not going to FL25 in a NA but i was there and there was plenty of power to go up to FL20.
Its probably not a situation thats going to come up a lot for most people but for us mountain dwellers there are times when it does.
I’ll be interested to see what you all think. Has anyone gone higher i have to think some people have judging from how ready the plane was to do it.
Blu

#3 - Turn around - even if you had TKS it’s useless not FIKI

I fly a G3 Turbo and it’s often that I stay on the ground because its not FIKI. Hence, I’m looking to upgrade.

It’s not worth ANY risk as far as I’m concerned. These days, I cancel meetings, I reschedule, etc… I never need to be anywhere, absolutely no matter what…

Have fun.

3

Service ceiling, where ROC is <100fpm, and Vx=Vy, is defined by density altitude- in a cold setting, 17,500 is not limiting, so you could climb a little higher. Over 18 you’ll be IFR anyway, so you’d need a pop-up clearance- literally. And at -17C, the clouds might not deposit ice on you.
This would be a bad idea for a number of reasons. Stall speed approaches indicated air speed at altitude, and your angle of attack will be high, so turbulence or increased load would be dangerous. Autopilot stalls can sneak up on you at altitude.
The clouds rose to you. Can you be confident they’d stop here, just because you need them to? What is your plan if they don’t?
Can you afford a 30 bank to make a 180* if conditions worsen? Can you find evidence to support your decision in the POH?
Finally, how do you feel about being a test pilot at 17,500+ over a 4000 ft frozen cloud layer which descends into granite?
That’s too much drama for me.

4

Blu,

Rather than directly address your specific question I first want to clarify the difference between possible performance and a performance limitation.

The SR22 has a maximum operating altitude of 17,500 feet. This is in accordance with FAR 23.1527 which reads:

§ 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.

What this means is that Cirrus, or any manufacturer that wants to certify an airplane under Part 23 can choose to demonstrate (establish to the FAA’s satisfaction) the ability of the aircraft to operate safely up to whatever altitude they want. Cirrus decided to certify to 17,500. There are probably reasons why they decided on that altitude related to design requirements but I’m not familiar with those parameters. Nevertheless the reason for that decision doesn’t matter.

What matters from the regulatory standpoint is that 17,500 becomes an OPERATING limitation. Because it is an operating limitation you MUST follow it. The requirement to do so is FAR 91.9:

§ 91.9 Civil aircraft flight manual, marking, and placard requirements.
(a) Except as provided in paragraph (d) of this section, no person may operate a civil aircraft without complying with the operating limitations specified in the approved Airplane or Rotorcraft Flight Manual, markings, and placards, or as otherwise prescribed by the certificating authority of the country of registry.

Trust me that paragraph (d) does not give you an out - it applies to helicopters.

The point of all this is that even if the airplane is physically capable of operating above 17,500 it is not legal for the pilot to do so. The same would be true if you didn’t have an IFR clearance above FL 180 or didn’t have a Mode C transponder in Class A or Class B airspace. The plane may be physically able to fly there but unless you comply with all the operating limitations imposed by the POH and the FARs it can’t do so legally.

Service ceiling as pointed out by others is a performance limit that occurs at that density altitude above which you can no longer achieve more than a 100 fpm rate of climb at maximum power and at best rate of climb speed. I believe this is at max gross weight but I don’t know how it is legally possible to get to that altitude if you departed at max gross since you burn fuel to get there. The point though is that service ceiling is NOT the same as a maximum operating altitude.

My answer to your original question given the terrain, below freezing temperatures to the ground, lack of knowledge about the bases and the OPERATING LIMITATION specified in the POH I would have enjoyed Saratoga, WY.

BTW, as a COPA member you are probably better off posting on the member’s side. You will get far more feedback there.

5

In reply to:

It’s not worth ANY risk as far as I’m concerned. These days, I cancel meetings, I reschedule, etc… I never need to be anywhere, absolutely no matter what…

Post of the Week nomination!

6

In reply to:

Service ceiling, where ROC is <100fpm, and Vx=Vy…

Actually, Vx=Vy at the absolute ceiling.

Back on point, I don’t routinely violate a plane’s operating limitations. It would take a real emergency for me to intentionally do so.

7

[quote]
Service ceiling, where ROC is <100fpm, and Vx=Vy, is defined by density altitude- in a cold setting, 17,500 is not limiting, so you could climb a little higher.

I did not know this. Thats what i was wondering about.
I was suprised at how good the preformance was @ 17500
I still had an IAS of 130. I could see across the undercast in question. visibility was excellent. There where no reports of ice for a 400 mile radius and the clouds in question gave no return on the doppler. But my understanding of the service ceiling was flawed i thought you where limited to 17500 regardless of preformance.
thanks for the info.

Has anyone went higher in a NA?

How High?

What was preformance like?

What where the conditions?

Blu

8

This is a good question. The POH limitations section states the aircraft’s service ceiling is 18,000 feet? Or does it state Max operating altitude? Service ceiling is not a limitation. It is a reference number. If you can still climb more than 100 fpm you haven’t reached the service ceiling. If you can still climb at all you haven’t reached the absolute altitude. Max operating altitude is a limitation and must be adhered to so as to remain legal. I am only familiar with the Turbo POH which states max operating altitude because you can still be climbing at 800 FPM at 25,000 feet.

EDIT: I looked up the TCDS and it says Max operating altitude, so to be legal you must remain below that altitude. Your service ceiling may be much higher.

9

In reply to:

Actually, Vx=Vy at the absolute ceiling.
Back on point, I don’t routinely violate a plane’s operating limitations. It would take a real emergency for me to intentionally do so.

Ed-

the Vx=Vy thing: I’m just not drawing a picture in my mind on this. Please enlighten me.

10

Sounds like you answered your own question.

The 17,500’ is listed under Operating Limitations, so that’s that.

As a historical note, it was originally 17,000’. Annoying eastbound VFR because it limited you (artificially) to 15,500’. General consensus is that the 17,000’ was a typo and it was later corrected.

11

[quote]
Sounds like you answered your own question.
The 17,500’ is listed under Operating Limitations, so that’s that.

So now i’m confused
U can’t go above 17500 or u can if your rate of climb is above 100 feet/min?

Blu

12

In reply to:

U can’t go above 17500 or u can if your rate of climb is above 100 feet/min?

Nope.

Just like you can’t load the plane to 3,500 lbs as long as you get a certain performance.

That’s the meaning of LIMITATION.

13

Here you go:
BTW, the SR22 will probably fly just fine at 17,501’ or at 3,401 lbs.
But the concept of “Most Conservative Action” precludes doing things that are probably OK.
1-300882-altlimits.jpg

14

Thanks for the clarification.

Do you know the reason for the 17500 limit?

It seems funny for the sr20 to have the same limit as the sr22 since the 22 has 50% more power.

To my limited mind it would seem logical that if the turbo is ok to FL2500. The SR20 is ok to 17500 then if the same standards where applied to the 22 it would fall somewhere in between.

Blu

15

In reply to:

Nope.
Just like you can’t load the plane to 3,500 lbs as long as you get a certain performance.
That’s the meaning of LIMITATION.

OK, but overloading above Max weight is a choice one makes while still on the ground. In the scenario Blu describes, one takes off with the best info available, weather is checked, but while enroute it closes in and clouds starts rising higher.

In the scenario as he describes, if one is forced to make a choice: With Positive speed, Positive ROC (400 fpm), either go higher, thru the 17,500 limitation, or descend thru the clouds, with the density altitude likely being below 15000 due to the temperature:

Question is; is that enough of an emergency to go thru the Max Operating Limits? If so, is it best to declare the emergency?

16

In reply to:

the Vx=Vy thing: I’m just not drawing a picture in my mind on this. Please enlighten me.

I can’t find a chart right now, but you can graph the decrease in Vy with altitude and the increase in Vx with altitude.

At some altitude they meet.

Let’s just say that Vy starts at 101k and Vx starts at 78k. For the sake of argument, let’s say they meet at 27,000’ in a NA SR22. And let’s say when they meet the IAS is 87k (guessing).

At that altitude 87k would be the speed for best climb AND best angle, and neither of them would result in a climb - by definition the absolute ceiling of the airplane. Any variance from 87k would result in a descent.

That help?

17

In reply to:

Do you know the reason for the 17500 limit?

I think it has to do with current certification regulations.

Similar planes certificated earlier have no such limitation.

Certifying a plane for 18,000’ and over has stricter requirements now - maybe someone more familiar can clue us in as to what they are.

18

In reply to:

I can’t find a chart right now, but you can graph the decrease in Vy with altitude and the increase in Vx with altitude.
At some altitude they meet.
Let’s just say that Vy starts at 101k and Vx starts at 78k. For the sake of argument, let’s say they meet at 27,000’ in a NA SR22. And let’s say when they meet the IAS is 87k (guessing).
At that altitude 87k would be the speed for best climb AND best angle, and neither of them would result in a climb - by definition the absolute ceiling of the airplane. Any variance from 87k would result in a descent.
That help?

Yup. I can envision it now. Thanks

19

Turn around.

20

In reply to:

Question is; is that enough of an emergency to go thru the Max Operating Limits?

Talk about subjective!!!

What do you think?

In reply to:

…if one is forced to make a choice…

No one was “forced” into that situation. If it gets to that point there was probably a chain of bad choices made to get it there.