Slam Dunk Approaches Tutorial

[Airbus]

;D

Looks like a fun technique to practice in X-Plane!

[flyinhawaiian]

That was superbly interesting, especially for those of us who might be flying in the midst of larger/faster aircraft where we need to keep our speed up.

[LA]

Something to keep in mind, is that the Mooney in the video has a constant speed prop. These props will act somewhat like a speed brake, which allows the plane to decelerate quicker while descending, than a fixed pitch prop can. I haven't found as much effect as I'd like in any desktop sim..............when it comes to the braking effect with C/S props. So.........I suppose results could vary.

LA

[flyinhawaiian]

Something to keep in mind, is that the Mooney in the video has a constant speed prop. These props will act somewhat like a speed brake, which allows the plane to decelerate quicker while descending, than a fixed pitch prop can. I haven't found as much effect as I'd like in any desktop sim..............when it comes to the braking effect with C/S props. So.........I suppose results could vary.

LA

Not necessarily.  In fact, a fixed-pitch prop would be better since they usually are at a lower angle of attack (read: more drag) at approach RPMs.  If you take a C/S prop and throw it to full forward at that speed, you might over-tach/torque the engine.  Good thinking, but lowering the gear will be much more effective at slowing you down

[LA]

Not necessarily.  In fact, a fixed-pitch prop would be better since they usually are at a lower angle of attack (read: more drag) at approach RPMs.  If you take a C/S prop and throw it to full forward at that speed, you might over-tach/torque the engine.  Good thinking, but lowering the gear will be much more effective at slowing you down

You don't push the knob full forward at that speed. Just leave it at 2350 or 2400, or so...... and the plane still slows. I know this because I've flown C/S props for around 18 years, and still have one these days. The C/S is all the difference in the world compared to a fixed pitch, when it comes to decelerating airspeed for the pattern. I don't go full forward, until the engine has really slowed down, as on final approach. To do so before....................is like jamming a vehicle into low gear at highway speeds.

I don't have retracts in my plane, and it's been too many years since I flew the retractable Arrow. I'd have to see more input, on which will actually have a better effect, between the gear & prop. Every retract I flew, always had a C/S.

I can easily 45 into a pattern at 150 kias, make a short downwind, tight base & still fly over the fence at 70 kias. I can decelerate at 2000 fpm down a mountain canyon, thanks to the C/S. An F/P simply won't do that.............unless it was optomized not to do anything else.

LA

[flyinhawaiian]

I'm pretty familiar with them too, and I see your point, but every time I've flown a plane with C/S prop controls, its had a retractable gear (about 5 years experience now - 12 total).  As soon as I hit Vle, I'll throw the gear down, and get slowed much faster than if I pulled it all the way back to 14-15" from 23"/2300rpm.  Constant speed props were designed to MINIMIZE drag in the cruise by increasing the angle of attack of the blade, thus showing a smaller cross-section to the relative wind.  The only way you're going to get that drag back is to advance the propellor control and decrease the angle of attack (aka larger x-section), which gets really nasty (as you pointed out). On the flip side, if I'm in something with a FP prop, especially on an aircraft equipped with a climb prop, pull the power back and the airspeed instantly bleeds off, and in my experience, faster than the other.  That said, I can't think of a fixed-pitch prop aircraft I've flown that had retractable gear, so it could have also been the fixed gear slowing me down as well (as in your case)...

I'll get a pretty good demo of this next Tuesday.  I'll be flying both types (fixed gear, fixed pitch prop vs retract/cs prop) back-to-back, so it should be interesting!

[LA]

Okay........I'm extremely familiar with C/S.  I bought and own one, for the numerous advantages over a fixed pitch. The ability to slow down much better than a F/P is one of them. We are not directly controlling prop pitch with the blue knob, as the prop governor does that. You do not have to push the knob full forward to get the braking/drag benefits.

If.................I had an engine out situation, and the prop is still turning (with oil pressure), I'd pull the blue knob all the way back to force it into coarse pitch. The less drag is very noticeable, to stretch a glide if needed. It's the opposite for most aerobatic C/S props......as they go to coarse with no oil pressure. Mine goes to fine.

LA

[LA]

I'll throw a bit more discussion in. Regarding fixed pitch & climb props..............you'll never find a fixed pitch prop for a "certified" plane, that will be set to the finer pitch that's obtainable with a constant speed. For instance, on the takeoff roll, the constant speed is allowing the engine to rev to it's full 2700 rpms. A fixed pitch will be several hundred rpms less. If it wasn't..........it would easily over rev in cruise, and you'd have to pull power back. The plane would just have to fly much slower than it's capable of. Fixed pitch props are a compromise. Depending where you fly, they can range from a better climb prop to a better cruise prop, depending on pitch.

Another item. Unlike a vehicle on a freeway, where you'd put it in fourth of fifth gear for faster highway speeds.................the constant speed prop is fastest when the knob is pushed full forward or nearly so. Once again, the governor is changing pitch, and it's not as if it's going to full fine. I pull mine back between 2600 & 2700 rpms for the best airspeed. But this means more fuel & more noise. I usually cruise at 2350..........as I have prop limitations between 2000-2250 rpms.

LA