Forum: F-35 Lightning II

Maybe I'm not crazy when I think to myself that F110 equipped F-16s are louder than F-15s. I've been here at luke for a couple of months now and I hardly notice aircraft taking off or flying around in the pattern. The CENC seems to be the loudest thing. I will say that 229s do sound different at idle from behind than 220s at the same power setting. Its almost like a lower pitched. But at take off I havent paid enough attention to notice a difference.

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I work across from the Lockheed plant at NAS FW JRB, I've thought the F-18 was loud when the Navy and Marines practice carrier landing training at the base, a few weeks ago when I was outside I heard the F35 take off for a morning test flight on take off its louder that a F110 equiped F16 and a F18 which both fly off NAS JRB.

Honestly, with 40,000lbs of thrust I wouldn't imagine this being a quiet motor. I wonder how the F136 will sound.

TimmayMan wrote:

Maybe I'm not crazy when I think to myself that F110 equipped F-16s are louder than F-15s. I've been here at luke for a couple of months now and I hardly notice aircraft taking off or flying around in the pattern. The CENC seems to be the loudest thing. I will say that 229s do sound different at idle from behind than 220s at the same power setting. Its almost like a lower pitched. But at take off I havent paid enough attention to notice a difference.

Isn't all the aircraft at Luke PW powered? or at least the USAF F-16s?

You must be crazy TimmayMan... Cheers

(but aren't we all!?!) If you've ever watched (listened) to a GE-129 and a PW-229 Viper take off one after the other the PW is much louder. I'll try to find my db charts for the noise... The exhaust velocity/temperature is much higher on the PW as well... PW-229s have a much longer/bluer augmentor flame.

Keep 'em flyin' Thumb

TEG

That_Engine_Guy wrote:

The high velocity exhaust stream exiting the engine "rubs" against the slower moving air around it, as this happens noise is created. When the stream is concentrated it takes longer for the air to mix and loose the "rub"

If you increase the surface area of the "rub" by using mixers, (giving a star or pedal pattern for example versus a simple round shape) the noise will be reduced as the exhaust stream will mix with and match the speed of the surrounding air quicker. (See the photo below for a "mixer")

Thanks for a good detailed explanation!

I have a follow-up question regarding the air mixing. Will an engine with good "mixing abilities" have a smaller IR-signature (leaving a smaller trail of hot gases) than an engine with bad "mixing abilities". In other words: Loud engine, higher IR-signature? Or are there no correlation between "air mixing" and IR-signature?

tgif wrote:

I have a follow-up question regarding the air mixing. Will an engine with good "mixing abilities" have a smaller IR-signature (leaving a smaller trail of hot gases) than an engine with bad "mixing abilities". In other words: Loud engine, higher IR-signature? Or are there no correlation between "air mixing" and IR-signature?

Forced mixing is done on some commercial engines predorminantly for noise reduction. It may have some IR suppression benefits, but whether it is significant depends on the threat. If the missile is a non-imaging plume seeker it probably does have significant benefits. If it is a non-imaging "hot metal" seeker, it probably doesn't do much. If the missile is a more recent model with a focal plane array, it probably doesn't help worth a damn.

The problem with forced mixing is that it costs engine efficiency and it is not particularly compatible with augmented engines.

Last flight from the south approach to NAS about 2 miles from middle marker where I live was close to 93 db with my hand held when the pilot throttled up with full gear down approach. Noise, well by some standards but nothing like the F-22 which is higher yet like around 102 on some approaches at EAFB.

That_Engine_Guy wrote:

TimmayMan wrote:

Maybe I'm not crazy when I think to myself that F110 equipped F-16s are louder than F-15s. I've been here at luke for a couple of months now and I hardly notice aircraft taking off or flying around in the pattern. The CENC seems to be the loudest thing. I will say that 229s do sound different at idle from behind than 220s at the same power setting. Its almost like a lower pitched. But at take off I havent paid enough attention to notice a difference.

Isn't all the aircraft at Luke PW powered? or at least the USAF F-16s?

You must be crazy TimmayMan... Cheers

(but aren't we all!?!) If you've ever watched (listened) to a GE-129 and a PW-229 Viper take off one after the other the PW is much louder. I'll try to find my db charts for the noise... The exhaust velocity/temperature is much higher on the PW as well... PW-229s have a much longer/bluer augmentor flame.

Keep 'em flyin' Thumb

TEG

Yes Luke is all PW. Ive been on GE 100 bases for the last 5-6 years and with the GEs I can feel them take off. PWs I hear them but no rumble felt. I do agree though that the 229s flame at AB is a lot more defined than the 100-129s up close, but when I was at Nellis I could tell the difference in sound of a GE vs a PW with the GE being louder.

Tell you what, the PW's may be noisy, but the power level at the mid frequency of the GE-132 can sometime be darn unpleasant to your inards at a location almost equal to the Aexit plane of the nozzle. Try it some times.

Talking about loud engines...................the RB-199's in the Tornado are right up there! As a matter of fact it can be a down right annoying sound! No offense to our British Cousins. Just something about it that just drives me crazy???

Shrug

Corsair1963 wrote:

Talking about loud engines...................the RB-199's in the Tornado are right up there! As a matter of fact it can be a down right annoying sound! No offense to our British Cousins. Just something about it that just drives me crazy???

Shrug

I have to agree … for such tiny motors, they wail in full burner!!! Very Happy

At the other end of the spectrum, you can stand out in the parking lot at LAX and watch a 777-300ER takeoff with two GE90s putting out 115,000 lbs of thrust each. That's a huge engine, and you can barely hear it over the ambient traffic noise. Now if we could just figure out how to put that much thrust into a fighter sized engine... Shocked

Meteor wrote:

At the other end of the spectrum, you can stand out in the parking lot at LAX and watch a 777-300ER takeoff with two GE90s putting out 115,000 lbs of thrust each. That's a huge engine, and you can barely hear it over the ambient traffic noise. Now if we could just figure out how to put that much thrust into a fighter sized engine... Shocked

The GE90-115B doesn't put out a lot of thrust for its weight and size. The engine also has a 128 inch fan, good like trying size intakes for it!

The GE90-11xx is a high bypass turbofan - it has a relatively slow exhaust velocity velocity as compared to fighter engines. It's actually one of the quietest engines in the sky. Far quieter than a 747. The most efficient, engine in the sky too. Laughing

Dwighlooi; I've flown straight turbojets like the J-79 and very high bypass fans like the CF-6, so I do recognize the impossibility of using the GE90 as a fighter engine. I just wanted to point out that the amount of thrust vs noise produced can vary widely, as Corsair said with the RB-199. I think that the T-37 produced more decibels per pound of thrust than any other airplane in existence, and the GE-90 produces the least decibels vs thrust.

In line with the subject of this thread, it does appear that the F-35 will be fairly high on the decibels:thrust ratio, especially when compared with the PW-100 and GE-110 series engines.

Forum: F-35 Lightning II

F-35 twice as loud as the F-15!