Military nicknames/ jargon

[A4K]

Thanks Doug for those!

Did the hawkeye get Hummer from the sound of the radome turning?
And what's with the A-3D? I'm guessing there were a few mishaps with them.

[DOUGRD]

Originally Posted by A4K

Thanks Doug for those!

Did the hawkeye get Hummer from the sound of the radome turning?
And what's with the A-3D? I'm guessing there were a few mishaps with them.

Hey A4K, Actually "Hummer" comes from the sound of the turboprop engines. The E-2C is the only carrier based aircraft with turbos.
The C-2A "Greyhound" also has the same Allison T-56 engines but it is not "Based" on the carrier but ashore and flys COD flights to the ship.

The A-3D was a good aircraft but like most early jets it had a slow "Spool up rate" which could be a real hazzard in the event of a "Low and Slow" wave off situation. I had a friend who flew the VQ version out of Rota, Spain for several years during the '70's and loved 'em. He does have a few hair raising tales to tell though.

Here's a semi useless fact for you.....What is the RPM of the Hummer's Rotodome............6 RPM.

Here's another....What are the first three aircraft launched off a U S carrier at the start of a normal first launch cycle of the day....
The Air Boss calls "Launch the Helo, the Hummer and the Hoover."

(I love trivia)

[A4K]

Thanks mate! I like to collect trivia too, hence the thread.

I'm showing my ignorance here, but by 'spool up rate' do you mean picking up speed?

[DOUGRD]

Originally Posted by A4K

Thanks mate! I like to collect trivia too, hence the thread.I'm showing my ignorance here, but by 'spool up rate' do you mean picking up speed?

"spool up rate" refers to the time lag between the moment the pilot pushes the throttle forward and the moment the engine has fully complied with the new setting.

Here's some more trivia about spool up ...I worked for Northwest Airlines as a line mechanic and along the way I qualified as a "Run/Taxi" mechanic. When I was training on the Airbus A-320 the trainers kept warning us to be careful with our throttle movements because the response time (lag) with the CFM 56 engines was EIGHT SECONDS! Think about it, that's a heck of a lot of time to be waiting for something to happen, especially in flight, say on final approach.

[A4K]

Dosen't sound too comfortable...! Is that due to it's size, or quality/ nature of the design?

Thanks for explaining the spool up rate, too. I thought that was what you meant, but wasn't sure.

[mkloby]

Originally Posted by DOUGRD

Here's some more trivia about spool up ...I worked for Northwest Airlines as a line mechanic and along the way I qualified as a "Run/Taxi" mechanic. When I was training on the Airbus A-320 the trainers kept warning us to be careful with our throttle movements because the response time (lag) with the CFM 56 engines was EIGHT SECONDS! Think about it, that's a heck of a lot of time to be waiting for something to happen, especially in flight, say on final approach.

Eight seconds!? If trying to waveoff that would seem like an eternity...

[DOUGRD]

Originally Posted by mkloby

Eight seconds!? If trying to waveoff that would seem like an eternity...

You're right mk! I think the early jet era must be when the phrase "Stay ahead of the power curve" was coined.

There's an Airbus inhouse film that really makes your hair stand on end. It shows a A-320 full of company employees flying around one of their fields.
It makes a real low pass and you can see it sinking. You just know the pilot is bending the throttles and trying to get some altitude. It goes past the camera and just before it crashes into the woods off the end of the runway you can hear the engines spooling up. Miraculously on one was killed.

[DOUGRD]

Originally Posted by A4K

Dosen't sound too comfortable...! Is that due to it's size, or quality/ nature of the design?

Thanks for explaining the spool up rate, too. I thought that was what you meant, but wasn't sure.

You know, I really have no idea except MAYBE it has something to do with the FADEC system (Full Authority Digital Engine Control) but I'm really not sure. The Boeing 757 has high bypass engines and doesn't have the lag time.

[A4K]

By high bypass do you mean it has a system that allows it to dump larger amounts of fuel into the exhaust to give it a bit of push while the engine is spooling up?

Sounds like a miracle no-one else was killed in that crash, too....

[mkloby]

All turbines, by their nature, have an inherent lag time... some worse than others, since exhaust gases pass through the turbine section which in turn drives the compressor - you can see the reason for the spool up.

[DOUGRD]

Originally Posted by mkloby

All turbines, by their nature, have an inherent lag time... some worse than others, since exhaust gases pass through the turbine section which in turn drives the compressor - you can see the reason for the spool up.

Very true and I think the CFM-56 takes the cake for lag time. On the other hand at Northwest we had more than our share of DC-9's. They have the JT-8 engines. During high power checks which are normally done after an engine change and for other reasons, one of the checks is to advance the throttle from IDLE to FULL power. The acceptable response time was 8 to 10 seconds.

A4K, an example of a high bypass engine would be like the JT-9 that are mounted on the 747. Big single stage fan in front which produces about 75% of the thrust. The other 25% is produced by the core (compressor and turbine) The term High Bypass comes from the amount of air which bypasses the core I think. Mkloby: correct me if I'm wrong here, OK?

[SoD Stitch]

Originally Posted by A4K

By high bypass do you mean it has a system that allows it to dump larger amounts of fuel into the exhaust to give it a bit of push while the engine is spooling up?

Sounds like a miracle no-one else was killed in that crash, too....

The phrase "high-bypass ratio" has to do with how much air passes through the compressor section of a jet engine and not through the turbine (second half) section of it; a "high-bypass" ratio means more air is dumped overboard before going into the combustor/turbine section. A good example of a high-bypass ratio engine would be pretty much any gas turbine used in a contemporary airliner; approximately 70% of an airliners thrust is actually derived from the eflux of the compressor section of it's engines, rather than the exhaust of the turbine section. In contrast, a low-bypass ratio engine sends most of the air it ingests through the compressor section and, thence, into the turbine section, with a fairly small percentage (20-25%) "bypassing" the turbine; a good example of a low-bypass ratio engine would be pretty much any military jet engine, in particular the Pratt & Whitney F-100 series and GE F-110 series engines.

On an historical note, the first "true" low-bypass ratio turbofan was the Pratt & Whitney TF-30, used in the F-111 and early models (pre-D) of the F-14; hence the "TF" (TurboFan) designation, versus "J" (J-57, -75, -79, etc.) for "Jet", used up until that time. For it's time, the TF-30 was remarkedly fuel-efficient though, since it was a first-generation turbofan (as opposed to turbojet), it had it's share of teething problems (including a low spool-up rate and susceptibility to compressor stall, which made it unsuitable for naval use).

[DOUGRD]

Here is an example of a High Bypass engine. If you look at the first stage fan and directly behind it you wull see the intake to the compressor. The compressor takes in very little air as compared to the initial volume drawn in by the first stage fan. (Sorry the picture is so big. If I was better at computing maybe I'd be smart enough to figure out how to down size it.)

[A4K]

G'day guys! Thanks for the explanations!
I must admit I'm pretty ignorant when it comes to the detailed side of engines (once again a big thanks to NZ defence cuts chopping me and 1100 other people out of the service during their training...)

[Bernhart]

how about fubar, snafu, or my favorite bohica ?