P-51D maneuvrability - what it was in reality ...

[ThomasP]

I may be wrong, but I think the main improvement (for the Merlin P-51) with the 4-blade prop was in climb. My understanding is that the mid-war Spitfire/Seafire went to the Rotol broad base chord 4-blade for the same reason - ie improved climb rate. The trade off was slightly less top speed. If what I have read is correct, the late-war Griffon Spitfire went to a tapered base blade to decrease drag of the center area at higher speeds.

There is a balance re the 'solidity' of a propeller blade arrangement. At high speeds the center area near the base of the blades does not contribute much to thrust and if the solidity is too high can actually create drag. The Rotol 4-blade of the mid-war period was better for climb and acceleration upto about 360 mph. The later tapered base blades were better for top speed beginning at about 380 mph, and hence also in high speed dives

Somewhere on the internet there are at least a couple of reports describing the effects of the mid-war Rotol broad base chord 3- and 4-blade prop relative to the improvement in climb and acceleration. I think one of them involved the Hurricane Mk IID, IV, or V.

 

[PAT303]

From what I've been able to understand the Laminar flow wing wasn't as good as it is made out to be, the reason being that manufacturing imperfections, damage, general wear and tear and even dirt and debris caused the laminar effect to be decreased so that's why I question it's overall effect, the real world is very different to a nice clean lab. Much is written about the 30mph advantage the P51 had over the Spit but how much of that is caused by the wing?, I feel it's the less glamorous drag caused by cannon barrels, blisters, stubs, tail wheel, exhaust and windscreen angle that has more of an effect on speed and drag between the two than the difference in the wings, as for maneuverability you only have to look at the Spiteful, the first one was a MkXIV with laminar flow wings, the overall consensus was it had worse handling than a standard MkXIV, particularly at lower speeds.

 

[Thumpalumpacus]

From what I've been able to understand the Laminar flow wing wasn't as good as it is made out to be, the reason being that manufacturing imperfections, damage, general wear and tear and even dirt and debris caused the laminar effect to be decreased so that's why I question it's overall effect, the real world is very different to a nice clean lab.

Those same issues would affect non-laminar wings as well. Which might you think would cope better?

 

[PAT303]

Those same issues would affect non-laminar wings as well. Which might you think would cope better?

That's true but from what I've read Laminar flow wings need to be perfect to work, and I mean perfect, dirt dust grass is enough to effect the laminar flow. I've never read anything other than a poor finish such as chipped paint causing issue's with elliptical wings which is true for every other type also.

 

[GrauGeist]

A laminar flow wing may be impacted by dirt, dings and such, but by virtue of it's platform, would still offer superior performance.

 

[Thumpalumpacus]

That's true but from what I've read Laminar flow wings need to be perfect to work, and I mean perfect, dirt dust grass is enough to effect the laminar flow. I've never read anything other than a poor finish such as chipped paint causing issue's with elliptical wings which is true for every other type also.

Oh, dear, we've got a rabbit-hole here. Didn't non-laminar wings suffer under the same problems? Also, the P-51 didn't even have elliptical wings, so I'm not sure what you're on about there, but it seems loosey-goosey to me. Here's a P-51; it doesn't, clearly, have elliptical wings:

Yeah, your protest here is unconvincing. Somehow dirt ruins P-51 wings, changes their shapes, and "dust" ruins the wing's aerodynamics. And the grass.

And none of this stuff blows off in the slipstream! It's stuck to the P-51's wing. But somehow that doesn't happen to other wing designs, on other airplanes?

But you don't even know the shape of the wings on a P-51.

 

[PAT303]

But you don't even know the shape of the wings on a P-51.

????? what are you talking about?, I never said at any point that the P51 has elliptical wings.

 

[PAT303]

Yeah, your protest here is unconvincing. Somehow dirt ruins P-51 wings, changes their shapes, and "dust" ruins the wing's aerodynamics. And the grass.

Maybe you should do a search on insect debris and it's effect on laminar flow wings, there's a huge amount of info out there. This paper is on the effects of anti contamination coatings on laminar flow wings, for such a non issue there is certainly a lot of testing going on. https://www.icas.org/ICAS_ARCHIVE/ICAS2012/PAPERS/865.PDF
https://ntrs.nasa.gov/api/citations/19880005572/downloads/19880005572.pdf NASA seems to think contamination has a significant effect on performance.

 

[GrauGeist]

Maybe you should do a search on insect debris and it's effect on laminar flow wings, there's a huge amount of info out there. This paper is on the effects of anti contamination coatings on laminar flow wings, for such a non issue there is certainly a lot of testing going on. https://www.icas.org/ICAS_ARCHIVE/ICAS2012/PAPERS/865.PDF
https://ntrs.nasa.gov/api/citations/19880005572/downloads/19880005572.pdf NASA seems to think contamination has a significant effect on performance.

For what it's worth, the P-51D operated from foreward operating areas during the war.

Their wings had contamination in the way of:
Mud
"Insect Debris"
Paint
Bird shit
Bullet impact patches
Dust/interstellar molecules

And yet, it still performed at a level that was virtually unmatched in the military, propeller-driven fighter capacity.

So, your point is?

 

[GregP]

Good grief! Can't you tell?

Me neither ...

 

[PAT303]

So, your point is?

I thought we were discussing the maneuverability and drag of the P51 and why it had less than contemporary fighters with some information on propellers and their effect on performance added as well?.

 

[pbehn]

From what I've been able to understand the Laminar flow wing wasn't as good as it is made out to be, the reason being that manufacturing imperfections, damage, general wear and tear and even dirt and debris caused the laminar effect to be decreased so that's why I question it's overall effect, the real world is very different to a nice clean lab. Much is written about the 30mph advantage the P51 had over the Spit but how much of that is caused by the wing?, I feel it's the less glamorous drag caused by cannon barrels, blisters, stubs, tail wheel, exhaust and windscreen angle that has more of an effect on speed and drag between the two than the difference in the wings, as for maneuverability you only have to look at the Spiteful, the first one was a MkXIV with laminar flow wings, the overall consensus was it had worse handling than a standard MkXIV, particularly at lower speeds.

As I understand it, if you allow 10 MPH to the wing, 10MPH to the cooling set up and 10 MPH to all the other stuff you describe it is pretty much in the 30 MPH ball park that is talked about. Any Spitfire is also affected by dirt, mud and paint peeling off too.

 

[PAT303]

As I understand it, if you allow 10 MPH to the wing, 10MPH to the cooling set up and 10 MPH to all the other stuff you describe it is pretty much in the 30 MPH ball park that is talked about. Any Spitfire is also affected by dirt, mud and paint peeling off too.

Absolutely which is why I feel the emphasis on the wings alone is overstated.

 

[pbehn]

Absolutely which is why I feel the emphasis on the wings alone is overstated.

Well misunderstandings are hard to avoid. The P51 was faster than the Spitfire and the P-51 had a laminar type wing but the difference in speed wasnt only due to the wing, which in fact wasnt laminar flow. The Spitfire picked the low hanging fruit, 4-5 years later NA picked up the baton looked at all there was being made and all the new tech available and produced a better design, it would be complete incompetence if they didnt. I am sure that if Mitchell had lived longer and Supermarine didnt have the pressures of fighting a war they would have produced something similar, Hawkers wouldnt.

 

[Thumpalumpacus]

Maybe you should do a search on insect debris and it's effect on laminar flow wings, there's a huge amount of info out there. This paper is on the effects of anti contamination coatings on laminar flow wings, for such a non issue there is certainly a lot of testing going on. https://www.icas.org/ICAS_ARCHIVE/ICAS2012/PAPERS/865.PDF
https://ntrs.nasa.gov/api/citations/19880005572/downloads/19880005572.pdf NASA seems to think contamination has a significant effect on performance.

From your link:

During flight tests on the Bellanca Skyrocket (ref.11, a representative insect'debris contamination pattern was accumulated by flyingfor 2.2 hrs at less than 500 ft above ground level at calibrated airspeed (Vc>equal to 178 knots.

That sounds exactly like high altitudes over Germany where the P-51 operated. How many bugs do you think are flying at 25,000 ft?

 

[Gunsights]

More info and commentary from the Quora community.

What are the disadvantages of laminar planes? What would be the best laminar planes and advances in laminar aerodynamic design nowadays?

Answer (1 of 3): First off, “laminar” is not a binary property applying to an entire aircraft. Almost every airplane has some parts where there is laminar flow. It’s just that some airplanes, and specifically some airplane wings, have more laminar flow than others. As others have pointed out, th...

www.quora.com

 

[BarnOwlLover]

As far as improving agility, could it have helped if the P-51 had a larger wing (Vampire or Sea Fury sized maybe), and was built from the start to British load standards (like the XP-51F/G/J, and P-51H)? The P-51H had similar power to quite a few Griffon Spitfires and was lighter than the 20 series Spitfires and Spitefuls (and had more range).

 

[PAT303]

From your link:

During flight tests on the Bellanca Skyrocket (ref.11, a representative insect'debris contamination pattern was accumulated by flyingfor 2.2 hrs at less than 500 ft above ground level at calibrated airspeed (Vc>equal to 178 knots.

That sounds exactly like high altitudes over Germany where the P-51 operated. How many bugs do you think are flying at 25,000 ft?

It's interesting that you aren't able to understand that they were trying to achieve, they tested at low level to increase the level of bug debris which is the purpose of the testing, they wanted real world data, likewise how do P51's get to 25,000ft?, are they just magically get there or do they take off from the ground and fly at low altitude, say 500ft first?.

 

[PAT303]

Well misunderstandings are hard to avoid

In regards to the Spit one of the biggest causes of drag is the one thing never mentioned, the angle of the windscreen.

 

[drgondog]

In regards to the Spit one of the biggest causes of drag is the one thing never mentioned, the angle of the windscreen.

Lednicer focused on the windscreen drag of the Spit IX and showed a stagnation region at the base of the P-51B windscreen in his CFD pressure distribution plots form VSAERO. IIRC he also speculated that the first indication of a Mcrit transition occurred there,