Why is manifold pressure important when landing a small plane?

Question

Why is manifold pressure important when landing a small plane?

Answer 1

i totally agree with john and calnicke

Answer 2

It isn't. Which may be why the smallest planes don't even have a MAP gauge. Besides, mainifold pressure is only required on a constant speep propeller equipped airplane to prevent an overtorgue of the engine when high prop pitch settings are used such as during cruise flight. If you are landing, the prop pitch is selected to it's flatest pitch setting so as to allow for a go around without the need to worry about overtorqueing the engine. So if you have a manifold pressure guage don't even bother looking at it during landing. You have much more important information the you need to know. And besides martin-n, what would be the correct manifold pressure setting to correct for a "high gust"?

Answer 3

It isn't.  You should be looking out when landing, not looking in at the "office".  

The only use a MAP gauge is is for setting the power with a v/p prop, or if it's a constant speed prop seeing what the engine is doing, for a constant-speed unit will endeavour to keep the revs the same no matter what power the engine is producing.

Answer 4

Like John said it is not important for the landing, when the power is off and it will read various things depending on landing speed, atmospheric conditions, prop RPM, etc.  If your eyes are in the cockpit as you land, you are looking at the wrong things.

Manifold pressure IS important for setting an approach.  On small planes with constant speed props, the props are put to high RPM before landing and typically stay at a high RPM unless the throttle is brought right to idle.  The manifold pressure gauge gives you an indication of how much power your engine is producing so you can set it appropriate to the type of approach you want to make.  

In my plane I use 13" with prop in fine pitch to give me a steep final approach without shock cooling the engine.  For a normal approach I use 15" and prop in fine and for a cruise decent I use 20" and 2300 RPM.  These will be different for different aircraft.

Answer 5

Hi Paul P everything that has been said is correct.

I was flying today 10/08/08 all that really matters is a correct approach and speed as well as wind direction.

Keep your head the cockpit is a busy place even in any small plane, flying is an art if you master it you join a very special group of fun loving people, as well as making friends who are friends for a long time, believe you me. just don,t give up if you fly.

Pete Glider Pilot

Answer 6

Manifold pressure is the actual indication of engine power output if the airplane is equipped with a constant-speed propeller.  Engine RPM is also an important measure.

So a pilot uses both indications to judge engine power settings with a constant speed propeller.  This makes manifold pressure important during landing approaches and landings.  Not all landings are made with the power all the way off.

This whole concept is rather large, and there is too much to say for this space.  Do an internet search on "aircraft manifold pressure."

And for sure "strong gusts" have nothing to do with manifold pressure, except that a pilot may need power at or near touchdown to correct for gusts.

Answer 7

when landing a small plane you are very susceptible to high gusts thats why manifold pressures important