Lakenheath/F15 Questions

[Skydiver]

So I've just had a second photography visit to Lakenheath and it's raised a few questions that I'm sure someone on here will know the answers to. Question 1, watching the F15s, they move from what looks like their hardened hangar area to a first staging area next to the runway on the south side. They seem to wait here for a while with ground crews moving around them. Some then move from here to the north side and wait at another holding area next to the runway, for some considerable time sometimes. Does anyone know what they're doing and why they sit for so long with engines running. Some seem to go straight from the first staging area on the south side and take off immediately. Question 2, The cool whistling sound they make as the exhaust outlets are increased/decreased, Is this connected to throttle position or moved independently? I'm assuming it's connected to throttle position but couldn't hear a correlation between the whistle and engine noise increase/decrease? Many thanks in advance, hoping someone knows the answers

[gamecock]

The cool whistling sound they make as the exhaust outlets are increased/decreased, Is this connected to throttle position or moved independently?

The nozzles are driven by motors operated by high pressure compressor air. The whistling noise is air exiting the nozzle exhaust motor. Tornado nozzle and thrust reverse control units (motors) make the same noise. They are not directly linked to throttle position, although (if it's like Tornado) they will move throughout the reheat range to maintain optimal low pressure turbine speed at all thrust settings.

[Skydiver]

Thank you Gamecock, perfect answer

[Snoop 95]

To attempt an answer to Question 1, Skydiver, the jets taxi from their own HAS to what is known as the Last Chance Point (LCP) which is where you see ground crew going around them. Their job is to remove pins holding external stores and to carry out a final inspection of all moving surfaces, pitot heads, tires etc. They then taxi out of the LCP and depending upon slot times, readiness of other jets in the group they either take-off straight away or taxi across the runway to the north side holding point to await clearance for departure. Incidentally the jets have to stop at a similar point after landing to have the pins replaced and to ensure the aircraft is safe to return to its HAS. Hope this helps.

[Skydiver]

Thank you Snoop, it all adds to the fun of watching these magnificent machines when I understand a bit more what is going on. Thanks for taking the time to enlighten me.

[page_verify]

If you want to Google more about what they do, look for mention of EOR (End of Runway) checks in the tech manuals (last chance is the British term I think?), there's some in the F-15 dash 3 here http://static.e-publishing.af.mil/produ ... f-15v3.pdf

[Thunder]

In contrast the Brits do everything on the line, before the jets taxi out.

[davekench]

Page_verify, that made very interesting reading thanks.

Dave

[Skydiver]

Thanks page_verify and Thunder for the replies, very helpful.

[Dan423]

To elaborate on question 2: the nozzle position is governed by the cenc, which is a lump similar to the nozzle motor found on the tornado. It's powered by air that is bled off the engine. It has a small exhaust nozzle at the 6 o'clock position (known as the donkey d1ck) and it is this that makes the whistling noise. It operates automatically depending on the pla (throttle) position read by the deec (ecu if you like).

You'll notice the noise being made while the aircraft are in the circuit too as the pilot selects approach idle on the mode control switch, the nozzle actuates and also does so on touch down when ground idle is selected, although this is automatic when weight is on the wheels.

[Skydiver]

Thank you Dan for your reply. Very helpful

[PA200]

Thunder wrote:

In contrast the Brits do everything on the line, before the jets taxi out.

We used too, but for some reason the Septic's got a little upset when our jets taxied the 2 miles down the Nellis ASP with the Flare pin removed!
These days if there are live stores involved it's an EOR team that will pull the pins.

Regards