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Aircraft Performance

Aircraft Performance Checklists

Next to a good preflight plan and current weather report is a thorough Weight & Balance/ Mass calculation. This is a matter of serious concern to all pilots as well as many other people involved in the flight. The pilot has to personally assume the responsibility (and by law) because he has control over both the loading and fuel management, the two variable factors which can change both total weight & balance.

This information is available to the pilot in the form of aircraft records, operating handbooks and placards in baggage compartments and or fuel caps. The owner of the aircraft has the responsibility to make sure that up to date information is available to the pilot.

Any change in weight & balance has its performance effects on the aircraft. For the pilot to have an overview of these effects we have developed the 'Aircraft Performance Checklist' below. It gives the pilot an idea what he can expect of his aircraft in the given circumstances.



Performance Prediction

Your ability to predict the performance of an airplane is very important. It allows you to determine how much runway you need for takeoff under certain conditions, if you can clear obstacles in the departure path, how long it will take to reach your destination, how much fuel is required and how much runway is needed for landing.

Weather also has certain effects on the aircraft, these need to be well understood. Think of density and pressure altitudes and the resulting loss of performance if these get higher than the actual altitude due to high temperatures or low pressure areas.

Together with performance prediction you also need to observe the operating limitations of the airplane. These limits establish the boundaries in which the airplane must be flown. These limitations apply to the airplane as well as to the engines. Think of limits on takeoff power, engine / propeller RPM, temperature of oil etc. You will find these operating procedures in the airplane and engine operating manuals.

Performance Checklists

The checklists below gives a quick overview on weather, performance and cruise data and for the intended flight. Use this in combination with the weight & balance form. You can use these quick reference notes (performance and weight and balance data) together with your knee board or put them on your panel so you be able to see them when you need the figures.


Weather Data


ATIS Information
AltimeterhPa/in.HgWind Directionatkts
TemperatureC/FCross windkts 
Pressure AltitudeftHead windkts 
Density Altitudeft   
Temperature aloftC/FWinds aloftatkts

Performance Data


Take Off:Landing:
Manifold PressureinHGApproach SpeedKIAS
Propeller SpeedRPMRunway Lengthft(m)
Fuel Flowgph/lphRunway Requiredft(m)
Rotation Speed VrKIASBest GlideKIAS
Take Off Distanceft(m)Maneuvering SpeedKIAS
Runway Lengthft(m)Climb SpeedKIAS
Initial Climb RatefpmAlternate Airport 

Cruise Data


Power55 %65 %75 %
Pressure Altftftft
Prop/MAPRPM/inHGRPM/inHGRPM/inHG
SpeedKTASKTASKTAS
Fuel Flowgph/lphgph/lphgph/lph

Manifold pressure RPM selection

Always select a MAP/RPM combination which gives you the lowest RPM and highest MAP for a given power setting. This is equal with selecting a higher gear in a car. It keeps the fuel consumption and wear (RPM) of the engine low and the pressure in the cylinder higher so the rings in the piston are seated properly and the engine is working the propeller in stead of the other way around.
Use the POH numbers and you will find that many over-square settings are acceptable. And this is also important: a lower RPM also means lower emitted noise from the overflying aircraft for those on the ground.

Conclusion

By filling out these numbers you will have more control over the situation. You know what to expect from your aircraft. If any of these numbers are not met (for example: propeller speed during takeoff roll or initial climb speed), then something is not right. Look for the cause before anything nasty happens. Remember: Takeoffs are optional but landings are pretty much mandatory.

Written by EAI.




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