N13HP down?

[Dudewanarace]

Re: N13HP down?

You should consider using the stops for thier intended purpose.

Not trying to keep this going, but I can't resist.

I'm trying to help you by making this statement: your still wrong. I'll take your word that you have rebuilt a few props in your day, and 'know how they work', but you are mistaken how they are applied.

Based on your description, lets say I set 2700 rpm on the ground for takeoff. For conversation sake, lets say that is full forward on the prop lever. Now lets say I'm going 220 KTAS, with the prop lever full forward, still showing 2700 rpm. Your saying the blade angle is in exactly the same place? On the 'pitch stop'?

I have a number of ways to show this isn't true, but I'll wait for an answer.

[Snidely]

Re: N13HP down?

I suppose it says something incredibly special about the aviation industry as a whole, and the warbird group in particular, that while we may not have known Ray Hofman (as I did not), news like like comes like a kick in the gut, regardless.

CAVU in your eternal flight west, Ray. Thoughts and prayers with family and friends.

Well said. True for me as well.
Snidely

[AAFO_WSagar]

Re: N13HP down?

Also, always important to remember, the loved ones of those who pass, often frequent here.. not saying anything in this thread was off, just important to remember..

Thanks!

W

[IcePaq]

Re: N13HP down?

Not trying to keep this going, but I can't resist.

I'm trying to help you by making this statement: your still wrong. I'll take your word that you have rebuilt a few props in your day, and 'know how they work', but you are mistaken how they are applied.

Based on your description, lets say I set 2700 rpm on the ground for takeoff. For conversation sake, lets say that is full forward on the prop lever. Now lets say I'm going 220 KTAS, with the prop lever full forward, still showing 2700 rpm. Your saying the blade angle is in exactly the same place? On the 'pitch stop'?

I have a number of ways to show this isn't true, but I'll wait for an answer.

I am not saying that at all.

I am saying that prop stops are there to ensure the prop. cannot enter a pitch that won't allow the plane to sustain flight with a properly running engine.

In your description of an airplane NOT experiencing failure going 220kts, I am NOT saying that the prop is in the same place as it was during take-off.

That is defeating the purpose of the ability to change pitch and I'm not sure how you gleaned that from my statements above.

Here's an example.......

Let's contrast the merlin as used in a Lancaster versus it's usage in a mustang.

In the Lancaster, the stops allow for a substantially larger amount of pitch variation.

One reason is to allow this multi-engine plane to feather a prop in the case of that engine having trouble making useful power and needing to be shut down.........provided the systems are working well enough that you have control over the pitch at all in the case of an engine failure.

It has more than one engine and can sustain flight without all engines functioning but being able to fully feather a stopped engine has a benefit in less drag.

In the mustang, I don't ever see a situation in which feathering it fully will be of any help unless the engine is stopped and it's also likely a stopped engine will render any prop adjustments impossible.

Sure, it would help glide with a stopped engine but being able to fully feather a mustang's prop means the stops are set to allow it and that we've just added another possible failure mode that generates less thrust than what is needed to sustain flight............even with a fully functional engine behind it.

The stops settings are very different between the two planes discussed above.

If I were piloting a mustang and the prop went to full feather or fully flat, I would be cursing whoever set the stops as my engine lugged itself to detonation street ............... or generated not enough thrust to sustain flight at 3000rpms.

The stops are set for your application of the engine/prop package and your plane should be able to sustain flight anywhere within the range between the stops settings.

Yes, that means that precious metal shouldn't be using the same stop limits as a shackleton.

If your application is a race plane, you accept that the coarse setting for high speeds might put you into high manifold pressure/low rpms while flying slow with the prop stuck in that position and you accept that the pilot will have to adjust to the emergency by not trying to sustain slow flight if impossible but rather manage his descent with whatever manifold pressure/rpm ratio he can get away with to generate maximum thrust available from the hand of cards dealt him.

If your application is a race plane or any other plane, you should never have to accept that the fine setting is unable to generate enough thrust to stay airborne with a functional engine behind the prop.

A large prop. with an engine behind it able to swing said prop at 3000rpms should not be able to be set so fine that the plane can't maintain flight.

The stop is there to prevent that.

As mentioned above by someone else, some extra acceleration at initial roll might be able to be harnessed with a super fine pitch.

I'm not too sure that running a finer pitch than will sustain flight gives enough initial acceleration advantage when beginning your takeoff roll over a pitch that can sustain flight.

Pilot can use judgement to decide whether or not to enter in a situation in which he needs that small amount of extra acceleration to get out.

I'm sure people here have flown planes in which you cannot simply firewall the throttle even with the prop set full fine at takeoff because manifold pressure will become excessive at that setting.

Stops set such that you can maintain flight at fine pitch might prevent maximum rpm at initial roll.

The pilot can reduce manifold pressure to acceptable levels at initial roll in that case and accept that being able to apply less than maximum power is only for a short portion of the takeoff roll and that he will soon be able to increase power once the plane picks up speed.

The pilot is there to manage the rpm/manifold pressure relationship to get the most out of the package regardless of the word "automatic" being included when describing some propellors but the pilot should not have to deal with any settings that fall outside of being useful.