Runaway Prop

[Whiplash]

I was reading through some of the emergency procedures in the Mustang manual when I came across this:

 

 

Is it just me or is a governor failure one of the most common malfunctions that result from taking just a few hits. I for one wouldn't mind if my chance of a governor failure were slim to none like the manual suggest. Although, my guess is that the manual is only talking about normal failures and not damage due to enemy (sometimes friendly) fire. Even so, the governor is smaller than a pilots head and pilot kills don't happen that often compared to a governor failure... at least not in my limited experience. I don't want to sound like I'am complaining, I mostly just wanted to bring the topic up for discussion.

[HotTom]

It's not just you....

[sobek]

Even so, the governor is smaller than a pilots head and pilot kills don't happen that often compared to a governor failure... at least not in my limited experience.

 

Not to say there might not be something wrong with the hitbox, but the pilot is sitting in between a lot of steel sheets and behind the engine, and the cockpit windshield is quite sturdy also. The prop spinner is completely exposed, so there is definately a difference.

[MTFDarkEagle]

Note it says "FAILURE". That doesn't mean battle damage. Like Sobek says: the prop spinner is at the pointy end of the aircraft --> large chance of being hit.

[Merlin-27]

Note it says "FAILURE". That doesn't mean battle damage. Like Sobek says: the prop spinner is at the pointy end of the aircraft --> large chance of being hit.

 

 

This is sound thinking... If the chances of the governor being damaged weren't equally bad from shots originating from the 6 o'clock position. If you've flown much combat in the P-51D you have seen this many times.. and it appears flawed. Much like the frequency that the gunsight is lost during battle.

[gavagai]

This is sound thinking... If the chances of the governor being damaged weren't equally bad from shots originating from the 6 o'clock position. If you've flown much combat in the P-51D you have seen this many times.. and it appears flawed. Much like the frequency that the gunsight is lost during battle.

 

This.

 

Pilot kills are extremely rare while the gunsight and prop usually go from the first bullet.:music_whistling:

[Lo-n-Slo]

Not to say there might not be something wrong with the hitbox, but the pilot is sitting in between a lot of steel sheets and behind the engine, and the cockpit windshield is quite sturdy also. The prop spinner is completely exposed, so there is definately a difference.

 

Prop governor is much smaller than the spinner; the governor itself is quite small and sits on the side of the engine nose case and is protected by a fairly large percentage of the prop disc (the cuffed Hamilton Standard prop blades filled most of the disc area at the prop root) and spinner; the relatively fragile valves and oil galleries are located right in the center of the prop hub. The rest of what is in the spinner cavity if fairly robust - you'd be more likely to lose a prop blade than to lose governor oil pressure when these bits are hit and it would take something in the order of a 20mm HE cannon round to do that much damage.

 

The illustration below shows most of the pieces without the spinner, which would be about the diameter of the nose case and come out past the hub dome:

 

 

cheers

Lo

[Whiplash]

Note it says "FAILURE". That doesn't mean battle damage. Like Sobek says: the prop spinner is at the pointy end of the aircraft --> large chance of being hit.

 

I did note that as I mentioned the manual is probably not referring to battle damage. I was probably a little off though when comparing it to a pilot kill. I was not trying to say that a pilot kill should be more frequent. But it's like Merlin said, the governor seems to take hits equally as often from fire taken at the 6 o'clock position. I think I would just like to see more damage to the water coolant system or oil splattered over my windshield for example. I'm not even sure what system is producing the fluid or smoke all the way at the tip of the wing beyond the guns and wing tanks. Come to think of it being hit in the wing tanks seems to have little effect on my fuel supple, but that is probably because of the self-sealing tanks and if I were to be completely honest I'm usually dead or just a short flight from base at that point so it's not really a concern. In all though, I have to say the battle damage is modeled pretty well on the mustang. Even if the governor takes hits more frequently then I would presume I have to believe it happen as often to the guy I am shooting at. If I could make a change or suggestion it would be on the visual graphics of bullets hitting the plane and ultimately the cheesy fire ball that erupts once the plane has been dispatched.

[HotTom]

LOL, Whiplash shifts into the old soft shoe, back-peddles off the stage....

 

The prop governor does seem extraordinarily vulnerable and fragile, considering where it is mounted but that's a subjective call on my part. I have nothing to say it wasn't this way.

 

But...(there it is!)...I wonder if the devs might explain what data or anecdotes they consulted when making it so easily damaged by enemy fire?

[Whiplash]

LOL, Whiplash shifts into the old soft shoe, back-peddles off the stage....

 

Pretty sure you're the only one laughing out loud at your own statement there. Not sure where you see me back peddling but you obviously didn't read my first post correctly so I'm not surprised. Either way I appreciate your opinion of my post regardless of how meaningless it is. meanwhile, I wouldn't mind knowing how the devs implement any of the damage data.

[Swoop73]

The prop governor runs on engine oil. Get shot up and loose oil pressure and the prop probably goes to flat pitch. Also is supposed to happen if too long inverted "negative G's" as the oil scavenger can't pick up. Maybe they model this? Just wondering.

[Lo-n-Slo]

The prop governor runs on engine oil. Get shot up and loose oil pressure and the prop probably goes to flat pitch. Also is supposed to happen if too long inverted "negative G's" as the oil scavenger can't pick up. Maybe they model this? Just wondering.

 

Hamiton Standard props (as on the P51-D) go feathered or full coarse pitch when they lose pressure. You DO NOT want a full fine or flat pitch prop acting as a BIG airbrake when you lose a motor:(

 

The prop governor does use engine oil as its supply, but has its own internal pressure pump that produces the regulated high pressure oil that controls the pitch of the blades. As long as the engine system is supplying oil at any pressure above zero, the governor will function. Run the engine at zero oil pressure plus any flight sustaining power setting for more than a few seconds and there will be much bigger problems to deal with than a prop at full coarse :music_whistling::smilewink:.

 

cheers

Lo

[Whiplash]

Hamiton Standard props (as on the P51-D) go feathered or full coarse pitch when they lose pressure. You DO NOT want a full fine or flat pitch prop acting as a BIG airbrake when you lose a motor:(

 

This always made sense to me but I never thought it through completely. So during a governor malfunction the prop pitch is essentially free and subject to the forces exerted on it. For example during a failure, while the engine is still running, the spinning force of the prop cutting through the air over comes the drag force so the pitch is going to be really close to full fine. Which is why they call it a runaway prop. Once the engine fails and the drag force is all that remains it forces the pitch to full feather. Which it why you don't fall out of the sky like someone threw on the airbrakes.

[Lo-n-Slo]

This always made sense to me but I never thought it through completely. So during a governor malfunction the prop pitch is essentially free and subject to the forces exerted on it. For example during a failure, while the engine is still running, the spinning force of the prop cutting through the air over comes the drag force so the pitch is going to be really close to full fine. Which is why they call it a runaway prop. Once the engine fails and the drag force is all that remains it forces the pitch to full feather. Which it why you don't fall out of the sky like someone threw on the airbrakes.

 

Not quite that simple - some makes of prop go full fine when the oil pressure is lost, some go full coarse - depends on the governor mechanics. I was going from failing and possibly faulty memory saying the Hamilton Standards on a P-51 goes full coarse . The statement was based on my (admittedly limited) knowledge of the governor mechanism and having watched a number of deadsticks landings over the years at Reno. Will inquire to get a definitive answer from the warbird mechanics who will know for sure. I do know that the Rotol contra rotating props on the Griffon engined Red Baron went full flat when it lost all oil pressure, which slowed the aircraft enough that Steve Hinton was unable to make the runway, resulting in a crash that only by a major miracle he lived through. Pretty sure the P51 HS works the opposite, going full course, so the pilot with a dead engine has a reasonable chance of gliding back to a decent approach.

 

Also, I believe for props that could be fully feathered (e.g. most WWII era multi-engine aircraft), if the main oil supply was lost there needed to be some form of auxiliary oil pressure source to drive the blades to the full feather position.

 

cheers

Lo

[Whiplash]

A full course prop would cause a drop in RPM not an increase which is the case in the sim. You are also able to glide relatively well once the engine quits. So that tells me that the pitch is changing when the governor fails.

[Yo-Yo]

Hamilton Standard prop goes to fine pitch due to inertia forces.

Anyway, the prop governor you mentioned is not only the units that are shown on the picture. There are many vulnerable points that can cause prop malfunction as they get hit.

For example, oil system in general, oil channels to the booster pump, the booster pump itself, centrifugal unit, linkage to this unit, etc, etc.

 

Different kind of malfunction can cause different prop behaviour: it can go to fine pitch, to the coarse pitch or be frozen at the current pitch..

 

By the way, in the DCS oil viscosity affects prop operation. Try to cool oil down by opening the radiator and diving at idle. THen advance the throttle fully forward and watch the rpm overrev.

[Whiplash]

By the way, in the DCS oil viscosity affects prop operation. Try to cool oil down by opening the radiator and diving at idle. THen advance the throttle fully forward and watch the rpm overrev.

 

It never ceases to amaze me the level of detail you guys put into these sims. I'll have to test that out next time. Thanks Yo-Yo for your input!