Warbird Information Exchange

Hello all,
I've been a regular visitor here for several years and it is my 'go to' site for the latest news on warbirds and I thought I'd make my first post. I've been a fan of all warbirds since I was a kid..............several decades have passed since then! As with most of you the P-51 holds a special place in my heart but there are 2 things I've never been able to find an answer to. Maybe you could help me.

1. The lower nose cowling on most Mustangs feature the perforated intake however many aircraft have this intake panel blanked as a full panel. I've never found the reason for this.

2. The main gear wheel clamshell door construction includes a strip of aluminum running from top to bottom of the panel midway across it. Many aircraft show the doors completely unpainted while others have the doors interior green except for this panel which is often bare or highly polished. Any particular reason?

Niggling little details really but they've peaked my curiosity.

G'Day Boomer605,

1. The perforated panel is the air inlet for engine filtered air. There are two filters that feed filtered air to the engine, if you have it selected in the cockpit. I believe some people have opted to delete this as the mechanism and filter boxes are quite complicated.

2. The polished strip on the inside of the wheel doors is actually stainless steel and it serves as a rub strip for the wheels on main gear extension, especially emergency extension.
I won't go anywhere near the paint question...

In the P-51D/K "Erection & Maintenance" manual, the non-perforated side-cover panels for the carb air filter, are called "cold weather covers", and shown to have been supplied with and stowed within the aircraft from the factory, along with other miscellaneous equipment and hardware. Although some might see them present on a restored Mustang and think they are not-authentic, the more one looks at period photos of Mustangs during the war, one can actually find quite a lot of Mustangs with the non-perforated panels fitted, at one time or another - one of the most often-seen examples being that of Preddy's "Cripes A' Mighty 3rd", and a large amount of photos of 78th FG Mustangs show non-perforated panels fitted. In a photo of the Iwo Jima based P-51D "The Enchantress", you can also see that it has the non-perforated cover panels installed as well - which may have been due to the effects of the volcanic dust/sand on the island.



On the clamshell doors, the inner, largest stamped piece of aluminum was always either left in natural alu-finish, or painted silver from the factory (likely left in natural finish). Through period color photos, the stainless steel rub plates were either left in bare/polished finish, or almost even more prevalent - finished in chromate yellow primer (perhaps more-so on earlier ships).

Thanks for the quick replies! As a modeller and someone who is interested in the technical aspects of aircraft I was intrigued by these details and knew this would be the place to find the answers.

I noticed the non-perforated air intake panels on several other notable P-51D's as well. "Detroit Miss" has the panels painted red on the yellow nose and many 4th FG aircraft such as "Blondie" and "Sweet Arlene" also have non-perforated panels. Come to think of it, it seems that most aircraft with blank panels are mid to late model D's. I can't recall seeing them on any B or C's.

I'm still a little confused though. As seen on photos where the cowl panels are removed, the carb intake trunking runs along the bottom of the engine and the filters can be seen. Does this mean that normal carb intake air was sourced from the intake behind the propeller and alternately filtered air could be sourced from these side intakes? If so then what conditions would warrant either selection? I guess I'm trying to relate it to an automotive setup where engine intake air is always filtered. If these filters and selection mechanisms are deleted on modern restorations does this mean that unfiltered air is being used? Would'nt this negatively affect engine life?

I'm no Mustang expert (we have people for that...)

Yes.

Filtered (less efficient intake position and with the filter) on ground / in dusty take off / landing, unfiltered in flight where dust isn't likely.

I'm therefore thrown by John's suggestion that the filtered intake would be made non-functional because of coral dust on Iwo. Surely the opposite would apply?

_________________
James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com

I'm sorry I threw that comment in there - I had my mind on two different things. I believe the plate seen in the well-known photo of "The Enchantress", is one of the ground-installed plugs for keeping the dust/dirt/sand/ash or other debris from being blown into the filter from the sides.





There is a great photo of 352nd FG Mustangs taxiing during the Russia "Shuttle Mission", kicking up clouds of dust and dirt into one another, with a caption that reads something along the lines of "filtered air was required".

In some photos, the "cold air covers" can be seen to still have the original Alclad production watermarks spread across them, either a sign of 'how fresh' they were when they left the factory/supplied with the aircraft, or possibly machined at the base of opperations.

Regarding seeing more "cold air covers" fitted to P-51D/K's, it may be a result of the time-line, with more P-51D/K's in action during the fall and winter of '44/'45.

Not at all, John. Makes sense now.

_________________
James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com

The Air Filter Box is a PIA when servicing the Oil Filter Cuno on the P-51. It requires you to remove a large section of cowl former/induction trunk/filter box assy to drain the oil from the Cuno or, in the case of modern spin on filters, accessing them at all.
If you install a -9 Merlin in place of the -7 there are casted in bumps on the oil pan that will rub on the box.
The filter box is not used today and is installed on those A/C that worry about stock appearance.
I have several on a shelf upstairs.

_________________
Rich Palmer

Remember an Injured Youth
benstear.org
#64- Stay Strong and Keep the Faith

BOOM BOOM, ROUND ROUND, PROPELLER GO

Don't Be A Dilbert!

It’s also worth mentioning that the filtered air was used primarily for ground operations since the filtered air could not provide enough intake air to produce take off power. In the event filtered air was mandatory during high power settings or the selector was not returned to unfiltered prior to their initiation, spring loaded doors on the sides of the intake trunk behind the filter bodies were provided for additional unfiltered intake air from inside the cowls.
Regards,
John