P-51 upgrade by warbirds operator

[Archer]

Can someone please explain to me what "transport heads" are on Merlin engines and how they differ from the heads used on the wartime Mustang Merlins?

As posted by TempestNut here:

Transport heads were originally developed for the Avro York fitted with Merlin 24’s. These were the same engine as fitted to the Lancaster from about 1944 onwards. These were the most powerful of the engines fitted to the Lancaster 1 and were mirrored in the Lancaster III with 224’s from Packard. However the York had a greater life expectancy than the Lancaster and RR developed the 24T with improvement to the heads in particular to give a longer valve life. Up to this point development had concentrated on strengthening the pistons, improving the supercharger and better lubrication of the bottom end to improve performance.

Post war the Merlin 24T formed the basis of the 500 series that found its way into the Spanish built CASA CA2111. The 600 and 700 series engines were based on the 100 series that powered the latter Mosquito’s and Hornets, with vastly improved lubrication and were also 2 speed 2 stage engines. They were built exclusively for the civil market. It has been stated that the development effort expended on the Merlin post war was as large as that from 39 to 45, such was RR desire to gain a foothold in civil aviation with the Merlin.

[Pyog]

On the first question I'd have to defer to others with more intimate knowledge on the inner workings/operation, and I'm not sure if there is a clear answer on the second.

The "boosted" aileron trim tabs are linked in such a way that when the ailerons deflect upward the tabs will deflect downward and vice-versa, in a servo tab manner, helping "boost" the aileron in either direction when flying, making the aileron control forces lighter. Kermit Weeks' restored P-51D is one of those that is set up with boosted aileron trim tabs, and if you watch his P-51D "Kermie Cam" video on Youtube, where he does his pre-flight walkaround check, you can see that the trim tabs on the ailerons of his P-51D are set up that way when he moves the ailerons up/down. I'm not sure when that modification originally came about and I've heard it referred to as a non-stock feature. Most of the P-51D's I'm familiar with don't have the boosted aileron tabs.

I'm not sure which aileron rigging setting was most commonly used in original military service, but the reference and maintenance manuals of the period describe the three different rigging options available (10, 12, 15-degrees). Jeff Ethell described the P-51 ailerons as being "locked in cement" compared to the P-40, but that can depend again on how they're rigged I'm sure. In the Jeff Ethell P-51 warbird checkout, he described how his dad, who flew Mustangs in the late 40's/early 50's, flew Elmer Ward's restored P-51D "Man O War" and commented that none of the Mustangs he flew in the service ever flew that nice.

When the ailerons are rigged for full 15-degree deflection, I've read that you can have the stick all the way pressed against your knee, squished against the side of the cockpit, and still you won't have the ailerons deflected all the way to the stops. With the ailerons set up for 15-degree deflection, and boosted aileron trim tabs besides, it sounds like the roll rate really comes alive and with very light aileron control.

Mant thanks! I have watched again this video, and this is clear for me now!

There is a new TF-51d « lady jo » for sale on courtesy, and the annonce give some response to me, as this particular aircraft have a lot of upgrade:
http://courtesyaircraft.com/aircraft/n327db-north-american-tf-51d/

[Tourist-51]

I've seen some Mustangs with a door cut into the left side of the fuselage to make a small cargo compartment. I don't think this came from the factory, at least I've never seen a pic of a wartime airplane with such a door open.

The RCAF modified 18 Mustang Mk.IVs with a high pressure priming system (not sure when exactly).
A 2 gallon high volatile fuel tank was installed behind the cockpit and a square access door was added to the left rear fuselage where the top of the US national insignia would be.
It could be what you saw.

[JohnTerrell]

This is the RCAF mod, as can be seen on the restored "Ferocious Frankie" (former RCAF 9568), with the access door located in the upper side of the fuselage/top of the stars & bars (photos by David Witworth) for the high pressure priming system:
https://www.flickr.com/photos/dwhitworth/8464064749/
https://www.flickr.com/photos/dwhitworth/6851236584/

However, there is a civilian-mod compartment/access door added to many Mustangs flying today, located lower and nearer to the cockpit, to provide some extra storage and in some cases access to the re-positioned battery (on those with a second seat and the battery not located in the engine bay).

The most typical compartment/door modification can be seen in this photo of "Crazy Horse 2nd", located on the left side of the fuselage: https://www.flickr.com/photos/brikupfer/14797206630/

There is also this style, located on the right side of the fuselage, on a few examples such as "Little-ite" and "Scat VII": https://vintageaviationecho.com/wp-cont ... 3B7812.jpg

Mustangs flying today with the civilian-mod compartment in the fuselage include: "Crazy Horse", "Crazy Horse 2nd", "Excalibur", "Frances Dell", "Moonbeam McSwine", "Gunfighter", "Little-ite", "Scat VII", "La Pistolera", "Little Witch", "Mad Max", "This Is It", "Bald Eagle", "Nooky Booky", Yagen's "Double Trouble Two", "Lady Alice", G-SHWN, "Diamond Back", "Val-Halla", "Sweetie Face", "Quick Silver", and the list continues.

[bdk]

However, there is a civilian-mod compartment/access door added to many Mustangs flying today, located lower and nearer to the cockpit, to provide some extra storage and in some cases access to the re-positioned battery (on those with a second seat and the battery not located in the engine bay).

I believe this was a civilian Cavalier option that has been replicated by many operators over the years. Many have subsequently been removed during restoration to a more military standard.

[JohnTerrell]

That's correct, BDK. Here are some examples all with Trans Florida/Cavalier-mod history and different sized luggage doors, with "Moonbeam McSwine", "Hurry Home Honey" and "Ole Yeller" displaying the largest:

"Moonbeam McSwine": https://www.flickr.com/photos/kurtsj00/6139126650/
"Hurry Home Honey": https://www.flickr.com/photos/lawsonstone/2576570086/
"Ole Yeller": https://www.flickr.com/photos/sdasmarch ... 457769301/
"Cincinatti Miss": https://www.flickr.com/photos/nxgphotos/48661096432/
"Blondie": https://www.flickr.com/photos/aeropassion/49554435292/
"Val-Halla": https://www.flickr.com/photos/113942472 ... 483638681/
N151MC: https://www.flickr.com/photos/yesiwood/12470092515/

[ZRX61]

Stainless steel soup ladle gun port mod....

[Bradburger]

Very interesting thread.

I had wondered about mods to the ailerons, after Jeff Ethell mentioned (as John points out) that after his dad flew Elmer Ward's 'Man O War', he couldn't get over how light the ailerons were compared to how he remembered them on the Mustangs he flew. So the modification of the aileron trim tab to a servo tab (as per the Weeks example) would make sense on the Ward aircraft as well.

One mod I recall Jim Beasley mentioning on this forum was that some owners/operators have cut the elevator bob weight in half to reduce the elevator forces, which isn't too much of a surprise when with the standard weight fitted, a pull force of about 20 pounds per G is required!

I find it fascinating that on the first production D-5s (with fabric covered elevators and the horizontal stabilizer incidence set at +2 degrees), at roughly a mid CoG position, the elevator force was only 2.8 lbs per G, which is in early Mark Spitfire territory! With the 85 Gallon fuselage tank full causing an aft CoG, the aircraft was of course extremely unstable, and meant a reversal of stick force of -3.7 lbs! These figures are from Technical Order No. 01-60J-28 (dated 17th August 1944) which details the introduction of a 5.3 lb/g bobweight to all existing P-51B/Cs & D models with immediate effect, to help prevent pilots overstressing their aircraft at various loadings, and to help reduce the pitch instability with an aft CoG.

Of course on the later blocks of D models, a metal covered elevator was introduced along with a decrease in the horizontal stabilizer incidence (+0.5 degrees) and the bobweights retained, although I'm not sure if they were the same weight as T.O. 01-60J-28 specified.

(There was also a T.O. issued to install the metal elevators and decrease in horizontal stab incidence to existing B,C, & D models that had the earlier setup).

Cheers

Paul

[ZRX61]

Running propylene glycol coolant mix instead of the usual ethylene glycol mix to lower temps by 20deg, especially in desert areas... a small detail that was missed by the guys who flew that Spitfire around the planet last year resulting in it over heating pretty much as soon as it landed at Mojave. Also run the stuff in my Kaw 1100 & the fan hasn't come on in years (yes, it still works, I check it every few months for peace of mind)

[mazdaP5]

Old Crow B added a dorsal fillet that wasn't part of the original restoration.

[wolf]

Replace the Merlin with a Rolls Royce Dart 510

[bdk]

Running propylene glycol coolant mix instead of the usual ethylene glycol mix to lower temps by 20deg, especially in desert areas...

What brand/where do you get it?

[ZRX61]

What brand/where do you get it?

Sta Clean, truckers use it.
https://www.suremarineservice.com/Heat/ ... 1-840.html