Reason for RAF Mustang IV/IVAs having louvered filter intake panels?

[BarnOwlLover]

This is a feature I've seen on a lot of P-51D/Ks that were used by the RAF as Mustang IVs and IVAs. This feature wasn't used on the P-51B/Cs they got as Mustang IIIs, but only on a significant number of P-51D/Ks. I doubt they were delivered to them that way.

Was the a reason for installing louvers over the clean air filter intakes on those P-51s, and why it was adopted for earlier versions (or by the USAAF)?

 

[Engineman]

The intake RAM, Filtered or Warm airflow system varied greatly on different production types of P-51 versions.

Eng

 

[Wurger]

The intake RAM, Filtered or Warm airflow system varied greatly on different production types of P-51 versions.

Eng

IMHO it is about these ...

 

[BarnOwlLover]

I should've posted photos, but I don't have any good ones that show that feature. That is what I'm speaking of. As mentioned, I've never seen it on either USAAF P-51s or any type or on the P-51B/Cs the RAF used as Mustang IIIs. Only on RAF Mustang IVs.

 

[Wurger]

IIRC the reason was to prevent dust from being sucked in.This solution was particularly effective in field conditions, protecting the engine from runway dirtiness.

 

[BarnOwlLover]

I thought that was the reason for having a filter for the carb/supercharger intake to begin with (though they didn't have the screen, even the Allison Mustangs had air intake filters). Also IMO strange that the Mustang III never seemed to have the louvered filter panel, and the USAAF P-51s didn't use them, either (just the "cheese grater" ones).

 

[CATCH 22]

This is a feature I've seen on a lot of P-51D/Ks that were used by the RAF as Mustang IVs and IVAs. This feature wasn't used on the P-51B/Cs they got as Mustang IIIs, but only on a significant number of P-51D/Ks. I doubt they were delivered to them that way.

Was the a reason for installing louvers over the clean air filter intakes on those P-51s, and why it was adopted for earlier versions (or by the USAAF)?

Those "louvers" have been used on Mustang III as well. I believe as a retrofit. Many RCAF Mustangs III in No. 441 Sqn RAF (under RAF command, not in Canada) had them:

 

[Wurger]

As memo serves I have seen these also on the Mustang III. I would say that the RAF got the experience of the excessive getting dirt by the filters, especially because of the incoming dust with the propeller airstream . So they got the idea of the deflection of the dirty air flow beyond the filter suction area.

 

[Wurger]

Oh. I criss-crossed my post with Yves. ... just these images I have meant.

 

[CATCH 22]

Oh. I criss-crossed my post with Yves. ... just these images I have meant.

They are from an IPMS-Canada issue called RCAF 441 Mustang IIIs. Free for download from here.
Cheers!

 

[Wurger]

They are from an IPMS-Canada issue called RCAF 441 Mustang IIIs. Free for download from here.
Cheers!

Thank you Yves. .... I downloaded the PDF file some time ago.

 

[ColFord]

The issue of requiring additional filtering in extremely dusty, or very wet/icy conditions was identified on the Mustang III by the RAF in the UK. First became a notable issue when the RAF Mustang IIIs started operating from ALGs in France after D-Day where they encountered extremely dusty conditions which like happened with a number of other RAF types 'overloaded' the filter element, requiring more frequent replacement or cleaning. The other issue was some of the Mustang IIIs flying escort at lower altitudes escorting the Coastal Command strike wing Beaufighters and Mosquitos, where they entered into icing rain with certain areas of the airframe tending to catch and retain ice build-up longer - the NAA multi-hole perforated plate was one such area. The modification was a louvred plate that fitted over the NAA original multi-hole plate which would deflect heavier particles such as dust and icing rain past the filter intake area. By the time the solution was trialled, approved, documented and entered the supply chain, it coincided with the introduction of the Mustang IV, so as they were being prepared in the MUs and by contractors, before initial issue to RAF Squadrons they were the first to get them as a 'mandatory' modification. As Mustang IIIs cycled back thru GSUs, RSUs or MUs, then they would also receive them - this is why most of the photos showing Mustang IIIs with the louvred plate are usually from early 1945 onwards.

 

[Engineman]

Hi,
Here are some details about changes to the intake filter system.
Cheers

Eng