Engine cover

Unread postPosted: 24 Apr 2019, 10:39
by eloise
Why the engine cover of F-15, Su-27, Su-57, Mig-25 is silver looking whereas the engine cover of F-16, F-18,Mig-29, F-35 have a normal paint color ?

Re: Engine cover

Unread postPosted: 24 Apr 2019, 14:26
by mixelflick
The engine covers I've seen on F-15's are red. Most US tactical aircraft are, at least the ones I've seen on static display at airshows. Interesting story: An F-35 pilot who's plane was on static once told of how the engine somehow ingested that engine cover. But there was no damage to the engine.

And these were the "hard" engine covers, not the cloth type ones I've seen on other jets.

Re: Engine cover

Unread postPosted: 24 Apr 2019, 16:47
by eloise
This is the cover iam talking about:
10D417DE-FC7F-4640-90F6-B92B3AF09B53.png

Re: Engine cover

Unread postPosted: 24 Apr 2019, 17:18
by SpudmanWP
It's likely a heat issue. The spaces between the engine and the "cover" of the F-35 is actively cooled .

Air comes in via two wing scoops.

Image

It is vented through the outer gap that surrounds the engine nozzle.

Image

Re: Engine cover

Unread postPosted: 24 Apr 2019, 17:25
by eloise
SpudmanWP wrote:It's likely a heat issue. The spaces between the engine and the "cover" of the F-35 is actively cooled.

I don't think heat is the solve reason or the only reason
f-18, F-16 , Mig-31 also have normal looking paint in these area
B2AE5FEF-760B-4974-85D6-7124E8CD76D7.png

50BF2E13-57DF-4AD4-85E5-CCC85EA04887.png

0ED3CAB5-900A-4F8F-81D6-A7E851CCE0BB.png

Re: Engine cover

Unread postPosted: 25 Apr 2019, 05:17
by garrya
The unpainted area is made from titanium.
The majority of the aft fuse on the F-15 and Su-27 and Su-57 is titanium because their operating envelope involved very high speed and the engine nacelle temperature raised very high. Most paints that we use have bad adhesion with titanium and weathered very fast, It's not cheap paint they use either, at least in some major air forces it's now chemical agent resistant paint so it's expensive and toxic. Furthermore generally speaking there's no need to paint titanium since it resists corrosion (from engine leak oil) very well. Since titanium does not corrode, no corrosion protection, primer and paint is required, why add weight and complexity when it is not needed, we can just leave the area bare. The aft fuse on the F-16, F-18 and Mig-29 are aluminum so they need paint on it for corrosion protection. F-35 paint job is part of RAM , MiG-31 is a Mach 3 interceptor, and it uses a special paint to handle the extreme friction heat from air flowing over the plane.

Re: Engine cover

Unread postPosted: 25 Apr 2019, 06:13
by linkomart
On the early J-35 the metal under the engine bay was unpainted due to heat from the engine. I think there was a special paint developed that could withstand higher temperature, but don't take my word for it. On the J37 and J-39 increased ventilation of the engine bay solved that problem. Om the J-37, the bypass ratio of 1 also helped, because the engine were a lot cooler... until you hit afterburner...

my 5 cent.

Re: Engine cover

Unread postPosted: 25 Apr 2019, 06:14
by linkomart
J-35 =Saab J-35 Draken,
J-37=Saab J-37 Viggen and
J-39 = Saab Jas 39 Gripen, to be clear...