#### WK95

##### Well-Known Member

What is the service ceiling of a FlyCorvair or similar conversion engine?

- Thread starter WK95
- Start date

What is the service ceiling of a FlyCorvair or similar conversion engine?

This table give density in slugs per cubic foot because it uses the American system of altitude in feet, pressure in inches of mercury and temperature in degrees Fahrenheit.

While people often use pounds per cubic foot as a measure of density in the U.S., pounds are really a measure of force, not mass. Slugs are the correct measure of mass. You can multiply slugs by 32.2 for a rough value in pounds.

Altitude Pressure Temp. Density -

(ft) (in. Hg) (F.) slugs per cubic foot

0 29.92 59.0 0.002378

1,000 28.86 55.4 0.002309

2,000 27.82 51.9 0.002242

3,000 26.82 48.3 0.002176

4,000 25.84 44.7 0.002112

5,000 24.89 41.2 0.002049

6,000 23.98 37.6 0.001988

7,000 23.09 34.0 0.001928

8,000 22.22 30.5 0.001869

9,000 21.38 26.9 0.001812

10,000 20.57 23.3 0.001756

11,000 19.79 19.8 0.001701

12,000 19.02 16.2 0.001648

13,000 18.29 12.6 0.001596

14,000 17.57 9.1 0.001545

15,000 16.88 5.5 0.001496

16,000 16.21 1.9 0.001448

17,000 15.56 -1.6 0.001401

18,000 14.94 -5.2 0.001355

19,000 14.33 -8.8 0.001310

20,000 13.74 -12.3 0.001267

25,000 11.10 -30.15

30,000 8.89 -47.98

35,000 7.04 -68.72

40,000 5.54 -69.70

45,000 4.35 -69.70

50,000 3.43 -69.70

55,000 2.69 -69.70

60,000 2.12 -69.70

65,000 1.67 -69.70

70,000 1.31 -69.70

75,000 1.03 -69.70

80,000 0.81 -69.70

85,000 0.64 -64.80

90,000 0.50 -56.57

95,000 0.40 -48.34

100,000 0.32 -40.11

Source: Aerodynamics for Naval Aviators

Note: These are summary tables. For more detailed tables, consult an aerodynamics or meteorology textbook.

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So at an altitude with 1/2 the air as at sea level you will only be able to make 1/2 the horsepower that you could at sea level, unless of course you supercharge by one means or another.

Usually you are not going to cruise an airplane at much below 1/2 the naturally aspirated rated horsepower. There are exceptions of course.

For instance if you a looking to fly a plane that would be sufficient with 100 hp. on a good day,( but a bit lethargic on a hot day at altitude) then it would need approx. 55% (just over 50%) for your cruise hp. 'at sea level' (what ever that may be - perhaps 75% power). If your using 120 hp. that gives you a little leeway.

Lets first look at the weight of the airplane (in Lbs.) divided by 12 (formula provided by Mr. Hiscocks) to give the required hp. So for the Light Sports category a 1320 lb. airplane / 12 = 110 hp. (required for on a hot day at altitude). 120 hp. gives a little more power to work with, provided you achieve the rated hp. (advertised) at sea level.

So verify your confirmed advertised hp. and the hp. required -and take off 3% for every 1,000 ft. (loss of hp. for both advertised and required hp. - if there is a difference), until you get to that 55% you need for cruise and that should be the max altitude for cruise.

However getting there might be the problem as you have to climb to get there and as you get higher you climb rate falls off as altitude increases and power decreases.

But you should be able to work that out yourself, with this rough guide.

George

And it goes without saying the wing/fuselage is working under the same impediments...So at an altitude with 1/2 the air as at sea level you will only be able to make 1/2 the horsepower that you could at sea level, unless of course you supercharge by one means or another.

I get the sense that you are trying to compare the performance at altitude of a Corvair to the performance at altitude of a brand L or C.What is the service ceiling of a FlyCorvair or similar conversion engine?

if you are wondering if the performance of a Corvair run at 15,000 ASL suffers (as compared to its performance at sea level) more, less, or essentially the same as a L or C lifted from sea level to 15,000 ASL, the answer is: 'essentially the same'.