I’ve done most of my air travelling in commercial jets (32,000 feet), but I’ve had occasion to fly in a regional turboprop a time or two, and also a private single-engine plane a time or two.
At what altitudes do these two aircraft generally fly?
A Dash-8 has a cruising altitude of 25,000 feet.
‘Private single-engine plane’ covers a lot of territory. A J-3 Cub or an Aeronca Champ is good for ‘low and slow’. A Cessna 172 is good for moderate distances at an adequate speed. A Beechcraft Bonanza is good for higher altitudes and speeds. Most of my fixed-wing flying has been in a 172. From Lancaster, CA to Las Vegas we’d fly around 9,500 feet eastbound and 8,500 or 10,500 westbound. For reference, WJF is at 2,349 feet msl. For shorter flight you wouldn’t go as high.
Cruising altitude depends on the type and model of aircraft, the distance to be flown, whether it’s pressurised or if you have supplemental oxygen, weather, terrain, etc.
To fly above 12,500’ MSL for any length of time, supplemental oxygen or pressurization is required. Extremely few single-engine aircraft are pressurized, and probably less than 5% have oxygen systems on board. So most are not flying real high.
Regional turboprops certified for commercial operation have at least two engines. They are also pressurised. Further, they are jets - it’s just that, at lower speeds and alts, a propeller is more efficient. So the jet engine turns a prop instead of blasting air out of the back.
Typical altitude would be 20,000 - 25,000 feet.
Sorry, Xema edit window missed.
Yes, single piston engined planes are restricted in altitude. 9000 feet might be typical. Much higher than that would, as you say, require supplemental oxygen, which is uncommon.
True. But if you’re flying a high-performance single like a Bonanza or a Mooney you can get a portable oxygen system and a seatback carry case.
Is this a regulatory or practical concern?
Because there are plenty of people that live well above 12,500 MSL with no problem.
If the PIC feels comfortable doing it, is he allowed to go higher?
As Johnny L.A. noted, it’s regulatory. Also, some countries have different altitude requirements for oxygen. In Australia, oxygen is to be used above 10,000’ for flight crew and 14,000’ for passengers. So over here unpressurised aircraft cruise up to 10,000’. Parachute jump aircraft may go higher as I think you are allowed above 10,000’ for up to 30 mins without oxygen or pressurisation.
Many turbo-props have a ceilling of 25,000’. This is not necessarily because they can’t go higher but rather because the regulations require more supplementary oxygen for passengers above 25,000’.
Supplementary oxygen is that required in case of depressurisation.
The Australian requirements are to be able to descend to 14,000’ within 4 minutes and to have oxygen for either 10% of the passengers to last 30mins or for 20% of the passengers to last for 15mins. Obviously this is the same amount of oxygen, so the difference is in how it is distributed.
To fly above 25,000’ the aircraft must have oxygen for all passengers for up to 10mins or enough for 10% of the passengers for the entire time the aircraft is above 10,000’ (in the case of an emergency descent) or enough for ALL passengers for the time the aircraft is above 14,000’.
Aircraft flying above 25,000’ are also required to carry first aid oxygen.
The Dash 8 200 and 300 would not get much higher than 25,000’ even if it was allowed to–the 300 is a bit of a dog to be honest. Some other turbo-props (e.g., Dash 8 400) have significantly better performance and are only restricted by the amount of oxygen they carry.
Another concern for some piston engine aircraft is that their power reduces at high altitudes. Although the true airspeed of aircraft generally increases the higher they go, if the engines are not turbo-charged then there may be no benefit in flying above a certain altitude.
The Shrike Commander that I fly has a sweet spot around 6,000’ where the air speed achieved is the maximum for a standard 65% power setting. Any higher than that and 65% power can’t be maintained so the speed drops off. So although it can get to 10,000’ or higher, there is no benefit and I normally don’t fly above 6,000’ unless I want to avoid some weather.
It’s practical whether or not it’s regulatory. Yes, many people live above 12500 but theirlung capacity it greater than those who live at lower altitudes.
Having had some experience at flying at or above 12000 ft. without oxygen for 4 to 5 hours I can testigy that it’s a bitch. Physical effort leaves you puffing hard for quite a while. You can lose mental sharpness and become confused. The problem is that you live at low altitude and go suddenly to high altitude without any prepartion.
We had a series of missions at 14000 ft. which were quite difficult. There was considerable grumbling about it so the squadron commander fixed it. He called all flight crews up to the orderly room. There he said that if we were in any sort of physical condition the altitude wouldn’t be so hard to take. Therefore, effective immediately, all aircrews not actually on the loading list would take an hour of PT in the morning and again in the afternoon. The bitching came to an abrupt end. Never in the history of human conflict has the physical condition of so many been improved so much by so little exercise.
Problem is, I don’t know of too many single engine airplanes that would fly well at that altitude without some kind of turbocharging, regardless of how the pilot feels.
The regulation was written with the idea that most people don’t live above 12,500 MSL. For the US, it works pretty well as there isn’t a whole of inhabited territory in the country at that altitude. Tibet, I presume, would have slightly different regulations for practical reasons.