F-15 AB nozzles

Sorry if this was covered before but I always wondered why the nozzle actuators were exposed on the PW engines and not covered?

From what I have heard/read, the covering plates were removed for ease of maintenance. B-1 Lancers have them removed as well I noticed recently, probably for the same reason.

ThatEngineGuy or some of the other people that work closely in that department might have a better or more detailed(if allowable) explanation for you.

Stoli's right. The "Turkey Feathers" were removed because they were a PITA.

BTW, interesting screenname. Were you on FB's?

What you're seeing isn't the actuators, but the linkages and lever arms. (60 linkages, and 15 levers driving 45 segments and 45 seals) The 5 actuators are actually mount forward of the nozzle assembly around the aft portion of the augmentor duct.

But yes the external nozzle segments or "turkey feathers" as they are called, were removed for ease of maintenance. Note: F-15s of the IAF still use them, as do all the F100s in F-16s. I don't know why they don't use them on the F-15E w/PW-229s, as they are much simpler to remove.

Some of the "maintenance" issues stem from early nozzle crunches, and it was believed that removing the feathers 1; eliminated some binding from between the nozzles due to external air-flow between the closely spaced engines and 2; if it was easier to see the linkages with minor damage, more serious nozzle crunches and burn-throughs could be reduced.

If you have crack overhaul people doing your augmentor/nozzle maintenance in the shop, you'll rarely have nozzle issues, but they can still occur if specific parts fail.

Keep 'em flyin'
TEG

TC wrote:Stoli's right. The "Turkey Feathers" were removed because they were a PITA.

BTW, interesting screenname. Were you on FB's?

Thanks for the answer(s)! Yes I was a Crew Chief on FBs for about 10 years at Pease AFB (and LOVED every minute and ALL -111s)

In 1977 during the F-16 FSD flight test program, P&W engineers told us (GD test crew) the F-15s lost so many turkey feathers in flight, they suggested to the AF that the airplane be tested without the feathers. It turned out there was no significant difference in performance, so they were removed from all F-15s. So the maintenence problem wasn't access to all the nozzle mechanism, but replacing all the lost feathers.

The same nozzle on the same engine on the F-16 was not a problem.

Just put F110s in all the F-15s to cure that problem LOL (I'm biased, my father is a retired GE advanced engine programs manager).

I heard about the turkey feathers shedding in flight too.

I always wondered though what effect taking them off had on the IR signature. Obviously any IR rise apparently wasn't worth the trouble with maintenance and the like but still, there is a lot of hot metal exposed there now. The Israelis have chosen to keep them on so obviously there must be some justification.

All I know is that when the feathers first came off circa late 1970s/early1980s, it was a pain to model any modern Eagle out of the box because you'd inevitably have to go either scratch build new nozzles or buy a ready made set for some ungodly price (at least to a 12 year old kid). I ended up building two Israeli Eagles just for that reason.

Ski

darkvarkguy wrote:Just put F110s in all the F-15s to cure that problem LOL (I'm biased, my father is a retired GE advanced engine programs manager).

AFAIK they tried it at Edwards in the E models but had issues with the airframe not being strong enough with having 2x -110 GE's.

Interestingly enough though the E-Model engine bays are still configured to mount GE's in them, as well as quick access doors on the exterior.

The Korean F-15K has F110s.

Newer Ks are being delivered with Pratts, however.

TC wrote:Newer Ks are being delivered with Pratts, however.

Yeah, the 2nd batch of Ks will get the Pratt 229s. But I hear the Saudi F-15S gave the contract to GE for F110s and I think the F-15SG still has the F110s too.