Timeline for What prevents a small plane like a Cessna or Piper from flying as high as a jet?
Current License: CC BY-SA 4.0
20 events
| when toggle format | what | by | license | comment | |
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| Jul 4, 2021 at 4:09 | comment | added | Peter Kämpf | Yes - to show how this is literally true, use a 90° climb which is popular with model airplane builders. In that case, all lift is contributed by the prop. Intermediate climb angles are only linear combinations of a 90° climb and horizontal flight. | |
| Jul 3, 2021 at 21:06 | comment | added | niels nielsen | @PeterKämpf, is the vertical component of thrust in a nose-up climb what is referred to as "hanging the plane on its prop"? | |
| Jul 3, 2021 at 15:14 | vote | accept | Boeing787 | ||
| Jul 3, 2021 at 15:14 | |||||
| Jun 30, 2021 at 13:24 | comment | added | Zeiss Ikon | @RobertDiGiovanni Okay, not quite "in the coffin corner" yet, but not far from it if it takes TAS 400 to stay above stall. Yep, I was aware of Wiley Post's early pressure suit work (though hadn't understood it was a biplane he flew). I wonder if anyone has checked the Mach limit for a 172 (or maybe we should use a 175RG). | |
| Jun 30, 2021 at 12:18 | comment | added | Robert DiGiovanni | @ZeissIkon a biplane was taken over 55,000 feet in the 1930s. Biggest issues were cold and O2 for engine and pilot. But, with enough thrust to make IAS, a Cessna airframe would fly. TAS would be around 400 knots for an IAS of 65. I would add a second wing to the 172 and give it a shot with an electric motor. 60000 feet would be fine. | |
| Jun 30, 2021 at 11:04 | comment | added | Zeiss Ikon | @RobertDiGiovanni So you're saying if the powerplant were up to it, you could fly a 152 or 172 to 70k and be below Mach limit for the airframe, but above stall? TAS doesn't matter for stall, that's IAS -- and Mach goes to lower and lower IAS as the air gets colder... | |
| Jun 30, 2021 at 7:56 | comment | added | Robert DiGiovanni | @ZeissIkon the Cessna has a much lower wing loading than the U2. A brief check of a TAS calculator shows its Vbg airspeed no problemo at 70000 feet. | |
| Jun 29, 2021 at 19:35 | vote | accept | Boeing787 | ||
| Jun 29, 2021 at 19:35 | |||||
| Jun 29, 2021 at 18:24 | comment | added | J... |
You can add an air compressor (called a turbocharger or supercharger) to a piston engine's intake to trick it into thinking it is breathing sea level air - There's no trick here, by adding a compressor ahead of the intake you are actually feeding higher pressure air into the engine - no gags or tricks here, the plane thinks it is breathing denser air because it really is.
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| Jun 29, 2021 at 14:52 | vote | accept | Boeing787 | ||
| Jun 29, 2021 at 14:53 | |||||
| Jun 29, 2021 at 11:09 | comment | added | Zeiss Ikon | Add to this that a plane shaped like a typical Cessna will be near its Mach limit at stall speed not much if any above FL400. This was the limitation on the U-2 -- the airframe was Mach limited, and absolute ceiling was where you couldn't stay above stall at that Mach number. | |
| Jun 29, 2021 at 11:04 | comment | added | Peter Kämpf | Why should I add another answer when yours is already good enough? I would only link to lots of my older answers, like this or this one. I would, however, never say the plane needs to fly faster to produce enough lift for climbing. | |
| Jun 29, 2021 at 10:57 | comment | added | Peter Kämpf | @CGCampbell Thank you for pointing this out, but oddities like umlauts cannot be insisted on. I don't particularly mind the other spelling - it is used in my email addresses and credit cards due to the inflexibility of those. | |
| Jun 29, 2021 at 10:14 | comment | added | Nobody | @CGCampbell It's perfectly normal and acceptable to write ae instead of ä when you can't easily type ä on your keyboard or due to other restrictions. It's the reverse that is wrong, if something is usually spelled ae then you don't use ä. | |
| Jun 29, 2021 at 5:21 | comment | added | jamesqf | @StephenS: The 18K ft limit is probably because that's the level where everything has to be under positive control and IFR. 10K is NOT the ceiling for most small, non-turbo, piston aircraft. If it was, there are a lot of mountains hereabouts which you'd hit. 14K is a more reasonable limit. (Flying between here & the Bay Area, I'd usually use 10,500 or 11,500, depending on direction. And there are still a few nearby peaks higher than 10,500.) FWIW, I've flown into airports that were over 7500 ft elevation, for instance Copper Basin in Idaho: airnav.com/airport/0U2 | |
| Jun 29, 2021 at 5:20 | comment | added | niels nielsen | @StephenS, there are several factors at work. a plane designed to cruise above 10,000 feet needs an oxygen system and special navigation instruments because it's all controlled airspace up there. O2 and IFR nav aids are very expensive and complicate the business model for small planes. A 18,000 foot service ceiling is more or less typical for an unturbocharged piston plane but that same plane's best-performing altitude will be somewhere between 7,500 feet and 10,000 feet, which coincidentally does not require O2 or IFR instrumentation. | |
| Jun 29, 2021 at 4:16 | comment | added | John K | You can go higher if you add more supercharging stages. WWII fighters had service ceilings up into the 30s and some specialist aircraft with extended wings could get into the 40s. Problem is, for a civilian airplane you now need to pressurize it. Another limitation is cooling. The thin air becomes a struggle to get sufficient heat rejection from the cylinders and heat was a big enemy of the air cooled multi-stage supercharged engines above 30000 ft. It's not impossible but the various limitations make it impractical when jets do the job way better. | |
| Jun 29, 2021 at 3:38 | comment | added | StephenS | The modern turbo pistons I’ve looked at have a critical altitude of ~18k and ceiling of ~28k, and ~10k is most non-turbo pistons’ ceiling, so that makes sense. Is there a physics limit to how high we can make the critical altitude, or is 18k just a common target due to market factors? | |
| Jun 29, 2021 at 3:36 | vote | accept | Boeing787 | ||
| Jun 29, 2021 at 14:52 | |||||
| Jun 29, 2021 at 3:07 | history | answered | niels nielsen | CC BY-SA 4.0 |