Diesel motors are great...but?

[Egon]

At altitude the cabin air is heated which uses fuel. The cockpit area may have greater pressures than the cattle car section.

 

[John_Mc]

I've hand flown a piston engined airplane at just under 18K feet...no problem at all, but it had twin turbos and pressurization.

The highest I've been in my non-pressurized, non-turbocharged 180 HP Cessna 172 was 13,500 (going over a pass during a mountain flying course in Colorado). Not much to it, other than the rate of climb was slow. The fun part was landing in Leadville, CO. At somewhere around 10,000 ft above sea level, it's the highest paved airport in North America. It was strange landing at an altitude that was almost double my normal flying altitude.

 

[buickanddeere]

The aviation and nuclear industry requires that all components to be proven then certified. An expensive and laborious process. Outside of home built aircraft. Staying with the original factory spec spark ignition engine will be cheaper than a reciprocating diesel.
Small gas turbines already certified as APU on aircraft have been modified with pto drive to power a variable pitch prop.
Of course the tried and proven gas turbine for decades on "light aircraft" is the Canadian P&W PT6 and it's variants.
At most , more of the existing gas engines will be certified for UL 94 octane MO gas .

 

[Redneck in training]

Piston aircraft engines are pretty basic low tech machines but they cost just about as much as near luxury car that is way more complex. Is it a possible liability expense built in the price or it is because of market will pay the price or what else it can be?

 

[DarkBlack]

Nope....the AC was on. When you pressurize air, you create a lot of heat. When you're at high altitude the pressurization system is working to keep the cabin level at approximately 4-8,000ft. When outside air makes it to the bleed valves it'a already at high pressure, and around 400*F. It has to be run through AC packs (heat exchangers and air cycle machines) to keep temps reasonable in the cabin.

In simple terms, when pilots make the cabin warmer, they're simply turning down the amount of AC being used.

i'm no aviation expert, but I find it hard to believe that an airliner is cooling the cabin air when it's miles high and -50 degrees outside

 

[MossRoad]

i'm no aviation expert, but I find it hard to believe that an airliner is cooling the cabin air when it's miles high and -50 degrees outside

Air Conditioning doesn't mean air cooling. It means its conditioning the air.

The same thing happens in your car in the winter at -20 degrees if you put on your defroster. Your air conditioning compressor kicks on and helps to remove the moisture from the air. Even though you have it cranked all the way to the hottest setting, the air conditioner is running.

 

[buickanddeere]

i'm no aviation expert, but I find it hard to believe that an airliner is cooling the cabin air when it's miles high and -50 degrees outside

if you think back to high school physics class and the " Combined and Ideal Gas Laws". The compression of that atmospheric air from 2.71psi and -9F to 12.25psi cabin pressure will heat the air with the amount of energy require to increase the density by 4.5 times. Does the shop air compressor heat up when compressing air and the compressed air from the pump's discharge pump be above the inlet port temperature? How hot is the compressor discharge on the diesel engine's turbo while building just atmosphere of boost? That is why an intercooler is often used both reduce peak combustion chamber temperatures and into increase thermal efficiency during the compression and power stroke.

 

[k0ua]

How hot does the compressed air inside a diesel cylinder get? Just from compression it gets hot enough to ignite the fuel squirted into that chamber. Yes it is compressed a whole buch,
Something like 22 to 1 ratio, But I believe it illustrates the point. Daisy used to make an caseless ammunition rifle that used the compression of air that flowed around a small ball bearing to ignite the propellant charge behind the bullet. Yep no primer, no firing pin, just hot air to set her off.

 

[Egon]

In Focus: Breathing at high altitude - Lufthansa Technik AG

Maybe some informatiom

 

[Rock knocker]

I believe Egon should have the last word in aircraft AC, since he has supplied a definitive source.