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Service ceiling

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Service ceiling

Old 23rd Feb 2021, 08:20
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Service ceiling

Maybe someone can shed some light on a problem one of my students came up with...

Service ceiling is defined as 100ft per min climb rate.
Now I found a line at wikipedia that states
jet aircraft have a service ceiling of 500 ft per minute.

I can not find any information in a legal text, FAR, JAR or else.
Any help is appreciated.
Magictime is offline  
Old 23rd Feb 2021, 08:43
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Well your first problem is Wikipedia as it’s not an “official” source.
Second, jet aircraft may not be performance limited at their certified maximum altitude.
It may be a different limitation such as maximum pressurization differential or emergency descent requirements.
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Old 23rd Feb 2021, 11:23
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"Service Ceiling" (not called that)

1) Where to find it? Defined by the "environmental flight envelope" in the manufacturer's publications, e.g. Technical Specification.

2) How is it calculated? As B2N2 says there can be many factors. Climb rate is not a hard limit, that's why you won't find it in the regulations. Airbus talks about 300 ft per min as a reasonable number for flight management system considerations, but that's not a ceiling.
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Old 23rd Feb 2021, 14:58
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Off the top of my head service ceiling is as you say 100fpm for pistons. It is as your student says 500fpm for jets. I will edit with reference (and correction if necessary).
[edit: always thought it came from the FARs but have not been able to find it yet]

Last edited by oggers; 23rd Feb 2021 at 15:10.
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Old 23rd Feb 2021, 16:54
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The RAF Manual of Flying defines Service Ceiling as you say. Volume 1 Chapter 14 para 14.
Other definitions could be Absolute Ceiling: which I believe is how high you can get in level flight and Operational Ceiling which could be the maximum height permitted for all manner of other reasons. For example: max permitted cabin pressure differential, the max altitude it was tested to, the max height the Aircrew Equipment Assembly works to etc.
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Old 23rd Feb 2021, 17:36
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One of my bugbears. I can only find one reference to it in EASA documents, and that is a learning objective in the ATPL syllabus, and no definition provided. There is a reference to service ceiling in one old FAA doc., the airplane flying handbook from memory, and it turns up in one FAA regulation, something to do with oxygen, or two pilots (or maybe even autopilot). I suspect the definitions in Wiki have been written to match the answers in EASA exam questions.
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Old 23rd Feb 2021, 18:35
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Thanks to all of you.
I know that Wikipedia is no official source. My students came up with the problem and I could not solve it.
So if somebody eventually finds any legal text ....
If not I guess the service ceiling stays at 100ft / min for piston.
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Old 23rd Feb 2021, 18:55
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As far as your student is concerned:

The service ceiling is the maximum usable altitude of an aircraft. Specifically, it is the density altitude at which flying in a clean configuration, at the best rate of climbairspeed for that altitude and with all engines operating and producing maximum continuous power, will produce a given rate of climb. A typical value might be 100 ft/min (0.51 m/s) climb,[1] or on the order of 500 ft/min (2.5 m/s) climb for jet aircraft.
Wikipedia says it “might be” and offers no other reference.
Maybe explain to your student that service ceiling is still a relatively “useful” ceiling and the absolute ceiling is the airplane hanging on by its fingernails (aerodynamically speaking) and is nowhere close to optimal altitude ( for its weight) or economic sensible cruise altitudes.
I think your student is getting hung up on a definition rather then understanding the underlying reasons.
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Old 23rd Feb 2021, 19:24
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Looking back a long way, I remember nursing a Vampire T11 up to 49500 when I was filling in time at Valley after getting my wings at Swinderby in 1957. It took a very long time to get up there and the aircraft didn’t know it it was going too fast or too slow! The official service ceiling was 42800.

Last edited by brakedwell; 23rd Feb 2021 at 20:02.
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Old 23rd Feb 2021, 19:29
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Magictime, the only exam q I know of gives an engine out roc graph for a twin piston and asks the engine-out service ceiling. The secret bit of required knowledge is that, in the opinion of the guy who asked the question, that equates to 50ft/min. Service ceiling is no longer in the syllabus for the new '2020' exams..
Alex Whittingham is offline  
Old 23rd Feb 2021, 20:10
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I think the service ceiling is where it is expected there will be a 500ft/min rate of climb and is probably in CS25, I believe it was in BCARs. I do not have either docs to hand but will try and find them.
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Old 25th Feb 2021, 01:48
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Only reference I can come up with, pages 11-8 and G-27 of Pilot’s Handbook of Aeronautical Knowledge, FAA-H-8083-25B.
Service ceiling. The maximum density altitude where the best rate-of-climb airspeed will produce a 100-feet-per-minute climb at maximum weight while in a clean configuration with maximum continuous power.
The same seems to apply to jets when in a thrust limited condition.


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Old 26th Feb 2021, 12:04
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Thanks everyone.
I will give this to my class.
Let them find out more if they want to.
I checked for several hours all kinds of documents in the last few days and could not come up with a better solution
as you posted.
So thanks again and always happy landings...
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Old 26th Feb 2021, 16:49
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The single engine service ceiling is the altitude at which a twin-engine aircraft with one engine feathered can no longer climb at 50 feet per minute in smooth air.

Source: FAA
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Old 26th Feb 2021, 17:45
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I thought this thread was about commercial jet transports, all engines operating, for which the term "service ceiling" is hardly ever used in the real world. Ah Well ...
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