Forum: General F-16 forum

Why does the P&W F-100 on the F-16 have turkey feathers and the F-15 does not?

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The F-15 had them in the 70's, but they were later removed. From what I've heard, they were either redundant, or hindered the airplane's aerodynamic profile. The Eagle did look a lot better with them on, I'd say.

I know why the F-15 had them removed, just wonder why they did not do the same on the F-16??

medicdwpa wrote:

I know why the F-15 had them removed, just wonder why they did not do the same on the F-16??

My understanding it that they were not as reliable on the Eagle and prone to detaching due to aerodynamic influences in that region. The F-16 doesn't suffer from the same aero characteristics here.

Obi, you are exactly correct.

They be on GE powered Beagles Whistle

Obi_Offiah wrote:

medicdwpa wrote:

I know why the F-15 had them removed, just wonder why they did not do the same on the F-16??

My understanding it that they were not as reliable on the Eagle and prone to detaching due to aerodynamic influences in that region. The F-16 doesn't suffer from the same aero characteristics here.

2nd; The air flow between the two engine nozzles of the Eagle, coupled with the high speed exhaust plumes of each motor would cause the 'feathers' on the insides of the nozzles to wear prematurely and/or jam. Nozzle crunches were an issue and frequent inspections were required when the Eagle/F100 was first introduced. On the older F100s (Pre PW-229) the feathers were a pain to remove/reinstall.

By removing them from the Eagle it:
A. Eliminated jamming
B. Reduced maintenance costs (in both time and materials)
C. Allowed better inspection of the nozzle's moving hardware

On the F-16 you don't have the proximity of another engine or twin tails funneling air across two nozzles and exhaust plumes. The F-16 benefits more in handling and aerodynamics from having the feathers on.

Newer F-15Es w/PW-229s in the US could use them if they wanted, the F-15I is flying with them just fine.

Keep 'em flyin' Thumb

TEG

Proof yet again of what Neil Anderson (R.I.P.) used to say, "The best use of two engines is to build TWO airplanes".
fisk

Fisk,
Remember the stickers he had made up which had the shape of a shoe and said, "Help stamp out twin engine fighters"

johnwill wrote:

Fisk,
Remember the stickers he had made up which had the shape of a shoe and said, "Help stamp out twin engine fighters"

Yes, I may even still have one in the pile somewhere? I'll post a photo if I find it. Thumb

fisk

Speaking of turkey feathers and Vipers, back in 1997 or so we re looking at an initiative to modify the engines (I forget which manufacturer, GE or PW). The mod would add additional bypass cold airflow on the outside of the nozzle (reducing temperatures and therefore increasing turkey feather life) and also modifying how the turkey feathers were attached, simplifying R&R. The net result was expected to be approx a 60x reduction in repair costs per nozzle over the life of the engine. It was going to more than pay for itself...except we didn't have the funds for the initial investment so it was never implemented to my knowledge.

Wonder if anyone knows if this was ever picked back up...?

Haven’t seen any test for more bypass air over the nozzles. Only nozzles flaps I have seen damaged were from pilots using them as a landing assist. The ceramic coating inside the segments do wonders for heat dissipation.

Roscoe wrote:

Speaking of turkey feathers and Vipers, back in 1997 or so we re looking at an initiative to modify the engines (I forget which manufacturer, GE or PW). The mod would add additional bypass cold airflow on the outside of the nozzle (reducing temperatures and therefore increasing turkey feather life) and also modifying how the turkey feathers were attached, simplifying R&R. The net result was expected to be approx a 60x reduction in repair costs per nozzle over the life of the engine. It was going to more than pay for itself...except we didn't have the funds for the initial investment so it was never implemented to my knowledge.

Wonder if anyone knows if this was ever picked back up...?

The 'simpler' attachment is evident in the PW-229 Nozzle; the slip on bearing-posts & single aft-hinge bolt. That was already in the cards.

The 'cooled-nozzle' was part of the LOAN (Low Observable Axisymmetric Nozzle) program; they were going to use the 'advanced cooling' part to make the nozzle last longer (even if without the advanced shape or other new parts) You can see the 4 large round air inlet holes between each actuator in the nozzle support in the image below.

As for extending the life of the augmentor, that's been accomplished through the PW-229 program as well. When I began working F100s the nozzle TBO was 1200Hrs; then extended to 2000 cycles; the '97 Package' PW-229s came equipped with a 4300 cycle nozzle; now all the remaining PW-220 nozzles are being modified in the field at overhaul to a 4300 cycle configuration.

Don't know why they used axisymmetric in the name; pretty much any nozzle (including 2/3D nozzles) "have symmetry around an axis" Doh

Guess they needed an A to form the word LOAN? Shrug

Back to the point - the nozzles now last over 50% longer than they did in the early to mid 1990s, and the PW-229 Turkey Feathers are MUCH easier to remove/reinstall. So even though the LOAN didn't give the nozzle better LO attributes and the initial $$ weren't spent to save logistics costs, at least the latter has been funded through normal "support" funding. (Search for CIP continuous improvement program and your choice of engine type.)

See also: http://www.f-16.net/f-16_versions_article20.html

Keep 'em flyin' Thumb

TEG

That_Engine_Guy wrote:

The 'simpler' attachment is evident in the PW-229 Nozzle; the slip on bearing-posts & single aft-hinge bolt. That was already in the cards.

The 'cooled-nozzle' was part of the LOAN (Low Observable Axisymmetric Nozzle) program; they were going to use the 'advanced cooling' part to make the nozzle last longer (even if without the advanced shape or other new parts) You can see the 4 large round air inlet holes between each actuator in the nozzle support in the image below.

As for extending the life of the augmentor, that's been accomplished through the PW-229 program as well. When I began working F100s the nozzle TBO was 1200Hrs; then extended to 2000 cycles; the '97 Package' PW-229s came equipped with a 4300 cycle nozzle; now all the remaining PW-220 nozzles are being modified in the field at overhaul to a 4300 cycle configuration.

Don't know why they used axisymmetric in the name; pretty much any nozzle (including 2/3D nozzles) "have symmetry around an axis" Doh

Guess they needed an A to form the word LOAN? Shrug

Back to the point - the nozzles now last over 50% longer than they did in the early to mid 1990s, and the PW-229 Turkey Feathers are MUCH easier to remove/reinstall. So even though the LOAN didn't give the nozzle better LO attributes and the initial $$ weren't spent to save logistics costs, at least the latter has been funded through normal "support" funding. (Search for CIP continuous improvement program and your choice of engine type.)

See also: http://www.f-16.net/f-16_versions_article20.html

Keep 'em flyin' Thumb

TEG

Hi TEG, I am way out in the deep end of the pool but the axisymmetric reference could be to axisymmetric flow rather than physical geometry? I am not an engine guy nor have I slept in that motel where everyone wakes up an expert. Smile

fisk

TEG: Thanks for that update. Brought back a lot of programmatic memories. As for your question, in this case axisymmetric means circular (i.e. symmetric about the center axis of the engine) vice a square nozzle ala F-22.

Forum: General F-16 forum

turkey feathers!