Miss Velma P51 Landed in cornfield at Flying Legends

Thank you Archer, I thought my post may have been invisible. ; )

With regard to the MT blades made for the F-82 restorations, there are of course a couple of other limiting factors if one were to consider using these on other Mustang types – for one, that blade design was never in use on P-51A/B/C/D/K’s in original military operation, and thus a lot of owners would have trouble with seeing them mounted to their aircraft since it wouldn’t look period-correct – and second, these blades are made for use only with the Aeroproducts prop hub, not the Hamilton Standard prop hub. Not only would an Aeroproducts prop hub be required, but the nose cone/spinner is also of a different design and construction for mounting Hamilton Standard propeller hub/blades versus mounting Aeroproducts propeller hub/blades. Of course if there was such a dire need for Mustang propeller blades beyond current supply (which seems to be not an issue), it is wonderful that such an alternative option could be sought.

I had the opportunity to visit the Pat Harker F-82E restoration back in November 2015, and there was quite a bit of discussion over the development of these MT propellers and loads of testing required. Harker of course has all of the completed blades now for his aircraft (as does Reilly), but this prototype blade was shown to us as well, to demonstrate their construction. As I mentioned earlier, they are primarily made up of wood and resins, but then are covered in carbon fiber and painted. With this prototype blade, you can see it minus the carbon fiber/paint layers.

Fournier Boy, thanks for your additional information. I was basing this on US rules as I am not that familiar with the UK guidelines in this respect. As we are talking about a US type I figured that the FAA background would still be relevant. From what you explained, it seems that the original certification basis and approved mods are still the reference for any changes that you would like to make to your warbird. Unless you go to the trouble of having a Part 21 organisation develop a modification.

From the article posted by TonyT (and as mentioned by JohnTerrell earlier on), it seems that this is what was done to get an airworthy prop for the two F-82s currently under restoration. But please note that although the prototype MT F-82 prop was flown on P-51A “Polar Bear”, this was only part of the process to get the prop certified. It does not mean that a Mustang prop is available, although if you phone MT props, I’m sure they will happily quote you a price to get one. You would then have to go through the same process to get that one certified.

There are composite blades for the Mustang

https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&cad=rja&uact=8&ved=0ahUKEwjQ1-eA95fVAhUEPFAKHRBLBqAQFghJMAU&url=http%3A%2F%2Fwww.enginehistory.org%2Fmembers%2FConvention%2F2011%2FPresentations%2FModWarbirdProps.pdf&usg=AFQjCNEDTV7-cNO7INU_0PyYO2Af9w7IJg

https://generalaviationnews.com/2010/12/22/mt-composite-prop-flight-tested-on-warbird/

Same reason that most other modern aircraft do: strength, ease of manufacture, repairability…it goes on. Strange question – like asking why some aircraft have swept wings.

That’s a bad analogy. Swept wings provide lateral stability around the longitudinal axis (and lots of pressure equations to do with Reynolds numbers, and Mach related phenomena, before the real experts pipe up)!

Archer, this is fine if you are in the YSA on the N register – however generally ex-military types here were never issued with Civilian Type Certificates. Instead, they operate under airworthiness approval notes (AANs) which for the vast majority of warbirds here are individual to each registration (there are some blanket ones such as the chipmunk for example that has a broad AAN for civilian instructing operations on a CofA).

Generally the AAN for say a mustang or a Spitfire would state the aircrafts configuration against the original manufacturers build specification, and which military or existing CAA mods have been applied.

Modifications on an individual basis are permitted with each aircrafts AAN if they have been existing military or manufacturer modifications, or they have been designed and certified by a Part 21 design Authority and accepted by the UK CAA as either a major or minor modification.

So similar to an STC but not if you get what I mean.

FB

But as there are flying RR-Merlins with a composite prop, why shouldn´t a PA-Merlin not be able.

An aircraft type is certifed with a specific engine and prop combination, which is specified in the Type Certificate Data Sheet or TCDS. So it is not a question of whether a prop works on another Merlin installation, it is a question of whether that type is certified to fly with a specific prop, in this case a wooden one. If you do want to install a composite prop on a P-51, then you need to get a Supplemental Type Certificate that allows you to install the new prop on this specific type. Even though there may be advantages to a wooden/composite prop, the hassle to organise this probably doesn’t weigh up against the availability of new or new old stock P-51 prop blades.

For P-51s, as far as I know you can either register one as an Experimental or use the Limited Type Certificate that was originally held by Cavalier (now by Cal Pacific). This document is available here: http://www.calpacificairmotive.com/SubmittedToDesignServices/image/LTC-11__rev_5.pdf (see the bottom of page one for the allowed engine/prop)

Photo taken standing beside the A505 looking south towards M11

Rob [ATTACH=CONFIG]254801[/ATTACH]

Random question, but the airplane landed facing the A505 didn’t it? Anyone have any photos after it was in the field that show the direction it was facing? I was there that day, and my assumption is the airplane was facing the road, but I just figured I’d ask here to clarify for sure.

Not so strange, Sabrejet. There’s not much alternative to an aeroplane’s wings, but a wooden prop can potentially save an engine!

No, it is a completely different question! The advantage of a wooden prop on a historic aircraft with a very rare engine is quite obvious. The strength, the eaese of manufacture is the same with a modern composite prop. Those props saved some Mercedes engines within the last years. For the same reason, there are many Spitfires on their way with those props. The question may be the certification of the combination. But as there are flying RR-Merlins with a composite prop, why shouldn´t a PA-Merlin not be able. If you see the Twin Mustang, which is about to fly within the next years- it also has two composites produced by MT.

So, nobody knows why P-51s always seem to have metal blades then?

Same reason that most other modern aircraft do: strength, ease of manufacture, repairability…it goes on. Strange question – like asking why some aircraft have swept wings.

Non-official reports seems to indicate a fuel supply issue caused the loss of power.

The only advantage of feathering a prop is on a multi engine, it is a pointless exercise on a single as you are going to the crash site regardless and to carry the extra weight of a feathering mechanism and the added complexity is simply not what you want nor need on a single engined aircraft lol.

Welch’s Specialist Movements in St Ives was called in to recover the plane – but they got stuck at the lights because the wingspan of the aircraft was about a metre wider than the space between the traffic signals.

Julie Payne, the company’s operations manager, praised her staff for successfully completing the delicate operation to move the historic aircraft.

She said: “We left the field at 3pm, got to the traffic lights at 3.15pm then through the lights at 4.15pm and she arrived home safe at 4.30pm.

“The lights were 8.9m wide and wing span was 9.6m wide, our guys had walked and driven the route prior to moving, after many discussions we were given the go ahead by Cambridgeshire Police.

When we moved the aircraft around Saint Athan for the B of B show and Princess Anne’s visit, they were followed by workshops who cut down any road signs or lights as they passed and tack welded them back up afterwards, the process was repeated the other way, but properly welded back into place that time. They didn’t even cut the power to them and they were still flashing lying on the ground.

I would imagine that among the operators, a need for an alternative prop/blade type hasn’t been felt too strongly to-date. Each year, for instance, you see more and more cuffed Hamilton Standard prop blades, something that was considered extremely rare, at least on flying Mustangs, a few decades ago. Here in the US, there is an STC (Supplemental Type Certificate) that allows for the use of Grumman Albatross propeller blades on Mustangs, if an operator wishes to do so, otherwise I believe only the original specific Hamilton Standard and Aeroproducts propeller blades, as used in original military service, can be used on the Merlin-engined variants and still be registered in the Limited category (the accepted propeller blades and hubs are outlined in the P-51B/C/D/K Limited Type Certificate).

The only wood props that I know of that have been installed on a Mustang to-date are those which have recently been made by MT-Propeller, as copies of the original Aeroproducts paddle blades, for the F-82 Twin Mustang restoration projects. These prop blades, made of layers of wood, resins/composites, and carbon fiber, were installed and tested on the P-51 “Polar Bear” several years back, and they will be used on both of the Twin Mustangs currently under restoration to fly. For cost-point, it was the best route to take, having to re-manufacture a type of propeller blade that otherwise is next to unobtainable (namely for the opposite-turning side/engine) – when painted, outwardly they look the same as the originals.

I’m sure someone will be along with the definitive answer, but I believe one of the reasons metal is used in props, is that wood is limited to how much it can be shaped aerodynamically (even with the pressed wood process), and also how strong it can be made.

And of course, metal is not so prone to damage from the elements as wood is, especially when flying in rain or any other form of precipitation!

It’s worth remembering that some of the early Spitfire MK.IXs (F.IX) had the Dural props, as opposed to the more common Rotol Jablo/Hydulignum pressed wood types.

Cheers

Paul

Metal was more plentiful in America.

Ref #64 and #65 ,re feathering blades.both PM and the Seafire are running big engines,and`paddle-wheel blades`,so in the event of an engine failure you have probably a 50% increase in the drag,or greater if they windmill,and can give a yaw instabilty problem(flat plate effect),a very big`airbrake,so it is important to get the blades as `coarse` as possible,ideally feathered.Most feathering pumps run electrically off a small reservoir of oil,usually separate from the main supply.If the prop is feathered it will reduce your descent rate,giving you a better glide ratio,smoother airflow over the wings and tail,and much better control;and if one has to force-land it is better to crash under control than not.Just look at the PM at Reno incident with Thom Richard..

With ref to#73,it may well be that with wooden blades that there may be a C of G problem,as the aircraft was probably designed with them….

Because that is the prop it is certified with I would guess.

So, nobody knows why P-51s always seem to have metal blades then?

Thanks AF.

Cheers

Paul