I have an F-15 Question

[petebuilt]

I was working in Klamath Falls (Oregon) today. Several OANG F-15's were flying around, about 10 or so.

When they circling around, doing their individual approaches to land, I could here a (best I can describe) loud chirping sound, like a bird chirping.

It came from each jet as he made the turn to the approach.

They were probably at 300-400 feet above me. (I was on top of a Big 5 Sporting Goods building)

Does anyone know what that sound would be?

Thanks,

Pete Brown

[Spongebob]

It's the actuators for the exhaust nozzles, changing their shape.

HTH

Spongebob

[Jennings]

It's the super secret HAVE BIRD system. We could tell you about it, but we'd have to kill you :)

[petebuilt]

Sounds good to me! Thanks Spongebob!

Jennings, only you could come up with an answer like that! :)

[Ol Crew Dog]

I was working in Klamath Falls (Oregon) today. Several OANG F-15's were flying around, about 10 or so.

When they circling around, doing their individual approaches to land, I could here a (best I can describe) loud chirping sound, like a bird chirping.

It came from each jet as he made the turn to the approach.

They were probably at 300-400 feet above me. (I was on top of a Big 5 Sporting Goods building)

Does anyone know what that sound would be?

Thanks,

Pete Brown

It's the DEEC cycling through, spongbob was sort of right but its actually the Digital Engine Exhaust Controler. This control the primary nozzle actuator but the don' t make hardly a sound as they cycle, if they do then they at bad.

[falcon1974]

If what you say about the DEEC is true then every P&WC F100 in the Air Force inventory is bad. Every F-15 and F-16 I have ever worked on or have seen pilots playing with the noise lever have made that sound, even with the BUC. Also, the older -200s and -220s does not and did not have a DEEC. They were all EECs. The sound is from the exhaust nozzle actuator that has a mechanical flex drive and when the flex drives spin out the actuators it makes the chirping sound. If you ever see a G.E. F110 powered F-15 or F-16 and wonder why they don't make any sound is because the nozzle is hydraulic using fuel for the actuation. HTH.

[Ol Crew Dog]

If what you say about the DEEC is true then every P&WC F100 in the Air Force inventory is bad. Every F-15 and F-16 I have ever worked on or have seen pilots playing with the noise lever have made that sound, even with the BUC. Also, the older -200s and -220s does not and did not have a DEEC. They were all EECs. The sound is from the exhaust nozzle actuator that has a mechanical flex drive and when the flex drives spin out the actuators it makes the chirping sound. If you ever see a G.E. F110 powered F-15 or F-16 and wonder why they don't make any sound is because the nozzle is hydraulic using fuel for the actuation. HTH.

What is a "Noise Lever"?

When we manually cycled the actuators to get in sync with the EEC or DEEC there should be a smooth and silent movement. The DEEC and EEC have Flex Shafts that connect to the Primary actuatior on the Nozzle. If the Actuators are makeing a sound when the move then they could possibly be producing too much friction and slowing the nozzle, thus you snap the flex shafts. The sound is comeing from the DEEC or EEC cycling through. I worked on the F-15 as a Crew Chief, Engines and Hydraulics and even with the Flex Shafts discoed you will have that noise when running the EEC or later in the F100 life the DEEC. Part of the troublshooting tree is starting with the EEC or DEEC, disconnect the Flex Shafts and work back till you find the problem. With the EEC or DEEC out of Sync with the nozzle can cause anything from a Blowout to compressor stall. Next time your under the jet run your hand under the EEC/ DEEC exhaust and you get a nice rush of airflow, sometimes that would whistle as well. The DEEC and EEC both are fuel pressdure control but this pressure is transfered to the Nozzle Primary Actuator by way of the Flex shafts (that part of the Eagles Chirp as well).

Edited September 20, 2012 by Ol Crew Dog

[Andre]

What is a "Noise Lever"?

Throttle, most likely.

Cheers,

Andre

[geedubelyer]

Have a look at this vid. You can clearly hear the noise in question several times.

[Ol Crew Dog]

Throttle, most likely.

Cheers,

Andre

Ohhh.... never heard it called that, always been Throttle to me.

Thanx

[falcon1974]

http://www.f-16.net/f-16_forum_viewtopic-t-15879.html Here is a link as to what makes the sound. The noise lever is the throttle. Idle is minimum noise and to the fwd stop is maximum noise. The nozzle has nothing to do with the digital engine computer except for what position it is supposed to be in at what throttle setting.

[Doughboy]

-22's also make funny noises in the pattern but they sound more like a speederbike. They also sound crazy when they start up the APU. Here is a better video of the F100 noise. This guy keeps slamming the motor from full blower to idle so you can really hear it.

Edited September 20, 2012 by Doughboy

[Bigasshammm]

-22's also make funny noises in the pattern but they sound more like a speederbike. They also sound crazy when they start up the APU. Here is a better video of the F100 noise. This guy keeps slamming the motor from full blower to idle so you can really hear it.

That's one way to dry the tarmac.

Idk if I'd have the stones to stand that close. Wow.

Edited September 20, 2012 by Bigasshammm

[Ol Crew Dog]

http://www.f-16.net/f-16_forum_viewtopic-t-15879.html Here is a link as to what makes the sound. The noise lever is the throttle. Idle is minimum noise and to the fwd stop is maximum noise. The nozzle has nothing to do with the digital engine computer except for what position it is supposed to be in at what throttle setting.

Have you ever touched a jet engine before?

Never heard this noise thing you keep bringing up.

I worked on the F-15's Engines for 17 years till I was put in Crash Recovery.

The DEEC and EEC have everything to do with the Nozzle position, its not a Digital Engine Computer, its a Digital Engine Exhaust Controlller or Engine Exhaust Controller and it is attrtached to the nozzle actuator by way of 2 Flex Shaft.

The Throttle possition is cut-off, Idle, Max, Mil, and Augmentation, I have never in my 36 years in Aviation have called it a noise lever?

[falcon1974]

I will admit that the noise lever thing is a poor attempt at humor and sorry for confusing everyone. I distinctly remember hearing a deployment of mudhens at Andersen AFB and Lakenheath RAB shooting approaches for about 2 hours a day for weeks on end and also F-15Cs at Luke AFB playing with the lawn darts also making that sound. And yes, I have worked on F-16As and Cs Block 15+ and 32 models that had P&WC F100-220Es installed which is esententially an uprated -100 that the F-15C has. And yes I have an A&P certificate and unfortunately have to work on airplanes everyday for a major aircraft maker. I have been doing so for 15 years now both military and civilian. And ask what happens with an EPU that starts up that is not switched to bleed air only. Not fun. I have not heard of a DEEC for a variable exhaust nozzle so that is a new one for me.

[Ol Crew Dog]

http://www.f-16.net/f-16_forum_viewtopic-t-15879.html Here is a link as to what makes the sound. The noise lever is the throttle. Idle is minimum noise and to the fwd stop is maximum noise. The nozzle has nothing to do with the digital engine computer except for what position it is supposed to be in at what throttle setting.

The CENC(called sink) is attached to the Flex Shafts, the DEEC and EEC are what sends the signal to the CENC. AS stated the CENC is control with Air Pressure as stated in the link you sent me. So the DEEC controls the CENC electronically and the CENC controls the Flex shafts turning the Electronic signal into Mechanical input to the Primary actuator.

Its the CENC that makes the chirping soound, sorry been away from it, retired 12 years ago in November.

I have my A&P as well as 3 degrees,miss working on jets though, but still in aerospace, managment in the JSF program

Next lesson on the fun of changing a UFC, or how to stop the bleeding of a million safety wire cuts on your hands with JP-4 (or 8).

[Ol Crew Dog]

-22's also make funny noises in the pattern but they sound more like a speederbike. They also sound crazy when they start up the APU. Here is a better video of the F100 noise. This guy keeps slamming the motor from full blower to idle so you can really hear it.

We call that "Snaps and Boggies", take the jet out to the trim pad, put it on the hold back and pray the arresting hook is attached correctly to it.

[petebuilt]

WOW...I didn't know bringing up this question would be so controversial!

All very interesting though! I am learning a whole lot here!

They'll be very impressed with my "amassed knowledge" the next time I do work at the base! (ha-ha)

Pete

[falcon1974]

If you have any questions about a Williams FJ44 let me know 'cause I just went through a class on them. And no, they aren't just for cruise missiles anymore.:)

Kind of a neat little engine in a boring kind of way.

[Doughboy]

That's one way to dry the tarmac.

Idk if I'd have the stones to stand that close. Wow.

I came to Nellis back in like 97 or 98 when I was still in High School to visit my cousin. She worked in the P&W shop. They just got finished with a T-Bird -220 (chrome turkey feathers and supposedly souped up) and had to run it in the hush house that night. We went out there and they let me play with the motor. Then they took me out of the control room and walked me over to the stand. The dude told me to hold on to the cable as tight as I could. They put the motor in full blower and took some pics. I could have elbowed the motor I was so close to it. AWESOME experience! The heat from the afterburner plume was crazy but the wind coming from the baffles and down the tunnel was unreal!

[Ol Crew Dog]

I came to Nellis back in like 97 or 98 when I was still in High School to visit my cousin. She worked in the P&W shop. They just got finished with a T-Bird -220 (chrome turkey feathers and supposedly souped up) and had to run it in the hush house that night. We went out there and they let me play with the motor. Then they took me out of the control room and walked me over to the stand. The dude told me to hold on to the cable as tight as I could. They put the motor in full blower and took some pics. I could have elbowed the motor I was so close to it. AWESOME experience! The heat from the afterburner plume was crazy but the wind coming from the baffles and down the tunnel was unreal!

Imagine sitting in the cockpit doing snaps for 8 hours after refueling the jet with the hush house doors 3-4 feet off the radome tip trying to get it to blow-out, makes your spinkter tingle a bit don't it?

Edited September 21, 2012 by Ol Crew Dog