Descent Rates

[wyskass]

Hello,
Is there any reason for a real airplane to limit its descent rate, when doing a routine descent? Of course assuming, you're maintaining a safe airspeed, below the appropriate v-speed. Is there any reason I shouldn't just idle the engine, and descend at the maximum safe airspeed, even if it means 2500fpm? I was just wondering how this is done in RW.
Thanks,
Mike

[mdklatt]

[font size="1" color="#FF0000"]LAST EDITED ON Feb-04-02 AT 09:02PM (EDT)[/font][p]Well, if you're into severe sinus pain go right ahead and do that. The main limiting factor in climb and descent rates in an unpressurized plane is human, not aerodynamic. Anything above 1000 fpm in a descent is very uncomfortable because of the pressure changes. You can get away with higher climb rates, but that can still cause problems. If you have a cold or allergy problems, any change in altitude can be agonizing.

It should go without saying that you need to limit your descent rate close to the ground. The faster you descend the longer it takes to stop the descent, as some pilots discover the hard way.

[wyskass]

Thanks, that makes sense. This then brings up another question. What descent rates do airliners usually maintain? I used to feel alot of ear pain many years ago during landing, but it seemed to have stopped now, so I suppose it all depends on the individual.
Mike

[OStateFlyer]

Good engine operating practices also determine descent rates. For instance, pulling an engine to idle and pushing the nose over will subject a piston engine to shock cooling. Aside from that, arriving at the lower altitude where you want when you want will ultimately determine your descent rate.

Brad

http://www.okstate.edu/osu_orgs/flyingag/wings.gif

[mdklatt]

In a pressurized plane you don't have to worry as much about limiting your descent rates, but there are still limits. In a jet it's especially hard to keep your airspeed down in a descent. As ATC starts giving you speed restrictions you'll need to keep the descent rate in check. You can use the speed brakes if you get into a tight situation, but that's a last resort. If you have to come plummeting down like a rock that's a sign of poor planning, either on your part or ATC's. FS ATC can be bad about giving you slam dunk descents, especially in the faster planes.

One factor I didn't mention about descents in a small plane is the engine. Most airplane engines are air-cooled, and descending at low power may cool the engine too rapidly resulting in damage. This is known as "shock cooling". Turbocharged engines are especially fragile in this respect. You want to keep enough power in a descent to keep the engine warm, and this will limit your descent rate.