Expert: Heiko Hanusch - 11/1/2005

Question
Greetings,
I would like clarification on a few questions:
1. How would you define deck angle. Is it the angle between the flight path and chord foil or between the relative wind and vertical axis.
2. Do sweptback wings cause an increase or decrease in parasite drag OR increase or decrease in induced drag.
3. How many transponders are needed in RVSM?
4. L/D max on a jet gives maximum endurance or maximum range?
5. While holding at let's say 6000 feet, what would be considered worst on the performance of an aircraft: snow, freezing rain, rime ice or all

Thanks.

Answer
Hi jascha,

Thank you for your patience.
1. Deckk angle is the angle between the longitudinal axis of the aircraft in relation to the ground/horizon. During takeoff in a Jet, for example, we rotate to ~14 degrees nose up which produces a lift factor of about 8-12 and an observer next to the runway would see appr. 20-25 degrees of Deckk.

2. parasite drag is actually slightly less if the engine is mounted on the tail of the aircraft but can be higher with underwing mounted ones, but the wing itself, due to the sweep, has slightly less parasite drag (when compared to straight). When it comes to induced drag it can go either way depending on aircraft weight but as always it will become less as speed is increased. It also depends on what type wing you compare it to (tapered, plain etc.)

3. 2 are needed for RVSM  

4. it gives max. endurance

5. depending on the severity of each (light, moderate, severe etc.) but in general Freezing rain or freezing drizzle is the worst because it coats the entire airframe not just the wings, also no aircraft is actually certified  to fly in SEVERE icing conditions. Even a light icing encounter that is persistent over more than an hour could result in problems down the road. One uses ice protection to get out of icing as fast as possible even in a jet although you got some extra time there.