Altitude Effect on Performance - Details
Overall performance:
- Higher density altitudes increase takeoff and landing distances. By a reduction in weight you can regain some of the lost takeoff and landing performance at high density altitudes. Fly the airplane at no more than 90% of maximum gross weight. Take a Republic SeaBee at a maximum gross weight of 3600 pounds. 90% of 3600 pounds is 3240 pounds. Reducing the weight to 3240 pounds you would regain the lost performance.
- Higher density altitudes decrease the rate of climb and actual service ceiling. Decrease the maximum gross weight of the plane to 90% of maximum will increase the rate of climb and actual service ceiling. Multi-engined aircraft have good performance increases in takeoff, landing, climb and actual service ceilings. If you expect to fly mountain terrain often an investment in a multi-engined plane is a definite increase in safety margins. Turbocharged aircraft compensate for density altitude therefore their performance increase is less than non-turbo charged planes.
- True airspeed is higher than indicated airspeed. This is a visual illusion discussed earlier in a post about night landings. It can pertain to takeoffs in daylight. When your true airspeed is higher than a given indicated airspeed the pilot responds to the visual cues of higher ground speed he observes and rotates at a lower indicated airspeed than normal. The pilot is actually below his normal rotation speed. Rotating at an airspeed below actual rotation speed increases the takeoff run due to the illusion.
- Turning radius is larger at high altitude at a given indicated airspeed. Turning radius is proportional to the square of the true airspeed of your plane. Increase your true airspeed by 10% your turn radius increases by 20%. In a boxed canyon, in mountain flying, the increase may be too much for you to make the turn. You can decrease the radius of the turn by decreasing you true airspeed. This decrease in true airspeed will cause the plane to descend. If the terrain is too close you could crash. You can prevent the crash by increasing the bank of your turn. Be careful, decreasing your true airspeed and the angle of your bank brings you closer to a stall. Not a good flying decision if you didn't plan for it in the first place . Planning ahead is mandatory. The planes performance limits give you the information to calculate safe flying criteria. Passes, ridges, narrow canyons, weather, high winds and associated turbulence will affect you and your planes performance.
Flying in mountain terrain is great if you know your plane well and plan ahead.
