Is there a dive prop?

midwestpa24 said:
:yeahthat:

Nothing slows down and goes down faster than a turbo prop at flat pitch, or if allowable in beta or reverse. One turbine twin I used to fly could easily exceed 2500 fpm down at flight idle.
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I've exceed that in a seneca and a baron
 
@SixPapaCharlie - Just curious - to get down fast why wouldn't you aggressively spiral down vs nose dive? Maybe this isn't about a emergency and is about letdown?

For our 182 near VNE the elevator gets scary heavy. I only dare practice that up high so I can gradually pull back. Can't imagine letting down near VNE and thinking you could start to level off at pattern altitude!
 
Reverse in flight can really get you down in a hurry.
"The investigation into the crash revealed that the pilots had accidentally selected the propellers to reverse thrust while still in the air."
 
In the 425 I occasionally fly (turboprop), thrust levers to flight idle, props full forward, dirty...you are heading downhill in a big damn hurry
 
Albany Tom said:
Some planes have them, but they're rare because it's tough to pull out. So you need to install brakes:

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Thank you for that video. It explains how most modern day "journalists" obtained their aviation knowledge. ("good thing it had air brakes")
 
Unless you’re flying a slick RV that’s hard to slow down in the descent, there’s no need for a “dive prop.” Even then, just do an overhead and the added G forces will slow the aircraft to landing speed.
 
In a piston, using the prop to slow the plane is hard on the motor.
 
Kent Wien said:
The 3-bladed MT prop on a Husky is a dive prop. It’s the one thing it does best.
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Probably because you didn’t expound, this was generally ignored. The electrically controlled MT prop when set to high RPM does indeed act as a sort of speed brake - set at fine pitch adds resistance to airflow through prop rotating surface area.
 
SixPapaCharlie said:
So if I have a Grumman Traveler with an O-320 and a Grumman Tiger with an O-360, they would have different pitches?
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Possibly, but if they're both fixed pitch props in the same class (climb or cruise) the O-360 is most likely going to have a longer prop, probably something like 2" longer. Also, for the prop pitch, keep in mind the propeller is just an airfoil. If you increase the angle of attack (pitch) you're going to increase lift (thrust), but you're also going to increase drag.
 
RyanB said:
Funny, I’ve wondered that exact same thing. I still don’t understand how it works. Take for example a 150hp O320 and a 180hp O360. Both are turning the the prop the same RPM but one has a little more zippity doo-dah than the other… how? Maybe this is why I didn’t do well in physics class.
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Think your car's transmission.

Your 450 HP GTI doesn't accelerate well starting from fifth gear. But you knew that, because you tried once or twice.
 
Nothing out performs the normal envelope of a turboprop. Here is going down 2250 fpm at 96 knots pitched down 12.5 degrees at flight idle. On this flight I was held up on downwind to let an F35 pass under me, cleared to land and lost the almost 4000 feet required in under 2 minutes maintaining approach speed. :) Descent prop….. Check.

Now if you want to go down fast, point the nose down to 20-30 degrees speed up a little and put a little bank in there, and the mentioned 8000 fpm is quite doable. In a TP just remember to put some power in before level off, because you will quickly slow to stall speed. That has been the end of some TPs


CB4AF8DB-F562-433F-A4BA-CDD525E1D9BC.jpeg
 
Kenny Phillips said:
Your engine cannot likely spin a "cruise prop" at full RPM.
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The cruise prop is designed to allow the engine to reach redline at full throttle in level flight. That's how most fixed-pitch prop airplanes are delivered. What good is full rated power if you can never get to it except in a dive?

A cruise prop with too much pitch will overload the engine in the climb. Detonation poses a risk, with high manifold pressures and low RPM.
 
Many folks understand how a higher pitch requires more power.

A little tougher to follow is that for a given engine the sleeker airframe

has a lower Static RPM.
 
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