Warbird Information Exchange

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?

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.

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.

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.

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).

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?