EE Lightning question

Lightning Pressure Head/Pitot Static Tube

As Bri pointed out in an earlier message, the pressure head received pitot and static pressure. Pitot pressure entered at the tip of the pressure head. Set back from the the tip was a ring of small holes which received static pressure. Static pressure gives an indication of height. Before take off the pilot sets the local barometric pressure for ground level at the airfield (QNH) or the equivalent of sea level (QFE), any changes in height are then referenced to one of these datums.
The pitot and static pressures in the Lightning fed into transducers and electrical signals then fed into the Air Data Computer. In the ADC, static voltage signal (S) gave barometric height, pitot minus static (P – S) gave Indicated Air Speed and P – S divided by S gave Mach Number.
The position of the pressure head was intended to minimise the effect of the build up of the shock wave, however the height readings could be affected, even more than indicated air speed. This was exacerbated by aircraft attitude, which could be affected by the stores carried (missiles, fuel tanks, etc).
This may not have mattered too much in a Lighting climbing to intercept a target. However the Buccaneer used an almost identical Air Data System. The altitude indication error induced by movement of the pressure wave and different combinations of stores could lead to a variation of hundreds of feet on the altimeter. With a low level aircraft, this sort of height error could lead to a very deep furrow.

Sorry for the really noob question, but it will save me time searching….Im really getting into the EE lighting, and would like to know the purpose of the long rod type of thing that sticks out from the bottom of the air intake, Id assumed it was an inflight fuelling pipe, but i have just recieved a model of one, and the refuelling pipe is in another location!! 😮

The rod is the air speed indicator duct, in order to get a true resding it had to be outside of the influence of the aircraft fuselarge due to the distubances caused by the sircraft going through the sound barrier, you will see that all aircraft of that type have a similar fitting.
John H

If I remember my servicing course right, (it was a fair while ago) there is a line connection between the pitot and the over wing vent valves (OVV’s). If an OVV leaks internally, it can run through the line and drip out the end of the pitot. We are talking about an a/c that leaks out of every orifice imaginable.
Q: How do you stop a Lightning leaking?
A: Defuel it.

Thanks for that, I knew they were leaky, and that does make sense when some of the pressure systems are coupled.
I’ve seen Starfighters leaking fuel from every orrifice, usually when they were over fuelled!

John,
Thanks for the pic’s and Video links, lovely stuff 😀

Thanks for your help the other Saturday, I will be intouch 😉

MJR, what can I say, I thought about explaining all that but ‘lost the will’ while typing it out :rolleyes:

Be carefull what you say about 904 being the star, you know how 728 gets

See you soon guys

Date for your diaries, I will post these on the QRA thread as well:

April 26th, LPG open cockpit day (no running that day)

£8 per adult, kids £4, gates open at 10am
Basiclly come and see the two jets under cover for the first time, chat with us (if you want 😉 ) and our Lightning pilots, just come and take in the atmosphere, get close to the old ladies and take as many pics as possible

After that there may be a BAH open day at the end of May, more anon, when I know more

We are also planning an LPG 20th anniversary open day (20 years since Lightning operations finished and 20 years of us ‘messing’ around 😉 )
This will be in early July, but not confirmed yet

Cheers all:)

A mind of useless information:p nice pics John, 904 looks especially shiny, always the star of the show.

yup OVV datum chamber is connected to the static system so that the ovv knows when to vent @3psi over atmospheric. if the ovv internal chambers perish, tank vapour/fuel can leak back into the datum chamber and static reference lines, which also casues the ovv to continuously vent, and you get a nice white stream over the wing in flight:D how sad is it to know that off the top of yer head! LOL

As Micheal Caine would say, “and not alot of people know that”.

yup OVV datum chamber is connected to the static system so that the ovv knows when to vent @3psi over atmospheric. if the ovv internal chambers perish, tank vapour/fuel can leak back into the datum chamber and static reference lines, which also casues the ovv to continuously vent, and you get a nice white stream over the wing in flight:D how sad is it to know that off the top of yer head! LOL

You really should get out more:) . Funny though, some of the things you imagine would be easily forgotten once you get away from the job actually stick in your mind for the rest of your life. I always thought that when I got away from telephone engineering I’d forget the difference between the normal operating parameters of dial tone (48v d.c. @ 0.5amp) and ringing tone (250v a.c.- the amperage was never taught for some reason (makes frogs jump though)).

Here are a few to wet the whistle so to speak……

And a little picture video I made, accompanied by some Van Hallen…..

http://www.youtube.com/watch?v=fPN_2Dw2tQc

A video clip of mine, XS904 going full chat wth both burners lit up….

http://www.youtube.com/watch?v=Q-OMKBWbXOA

Comments welcome.

John.

“Come a see our two live one’s at Brunty “

I intend to ASAP , and i find the the QRA shed thread fascinating, And im sure its been said on this forum before but, you chaps that keep these aircraft servicable for people like me (noobs 😮 ) to see and learn about……deserve medals!!!!!

You learn something new every day!!!.

John.

If I remember my servicing course right, (it was a fair while ago) there is a line connection between the pitot and the over wing vent valves (OVV’s). If an OVV leaks internally, it can run through the line and drip out the end of the pitot. We are talking about an a/c that leaks out of every orifice imaginable.
Q: How do you stop a Lightning leaking?
A: Defuel it.

yup OVV datum chamber is connected to the static system so that the ovv knows when to vent @3psi over atmospheric. if the ovv internal chambers perish, tank vapour/fuel can leak back into the datum chamber and static reference lines, which also casues the ovv to continuously vent, and you get a nice white stream over the wing in flight:D how sad is it to know that off the top of yer head! LOL

Must be quite a job sorting them, i just wish we had some airworthy ones, mind you just watching them taxi is good enough. I want to go to south africa because they got a few airworthy ones.
here is a video from youtube, of lightnings in South Africa, it was filmed in 2006 it shows 2 T5’s and two F6’s

http://www.youtube.com/watch?v=4vjQe92-w_I

Interesting, how?

If I remember my servicing course right, (it was a fair while ago) there is a line connection between the pitot and the over wing vent valves (OVV’s). If an OVV leaks internally, it can run through the line and drip out the end of the pitot. We are talking about an a/c that leaks out of every orifice imaginable.
Q: How do you stop a Lightning leaking?
A: Defuel it.

Indeed, but it can leak fuel.

Interesting, how?

Its is yeh :rolleyes:

Come a see our two live one’s at Brunty 😉

Don’t worry Andy, you’re on my list of must visit places but it’s a matter of finding the time. Often the only day I can manage is a Sunday which you guys rightly keep aside to have some time with your families. If I have a Saturday off the other half usually has something lined up that prevents me from getting up there.

Being an instructor with 1011 Amesbury ATC at Boscombe Down I get to see (just) the gate guard, XL629, the only preserved P11-T4 in the world.
Whilst I understand getting permission to enter gate to photograph her is not difficult I haven’t yet ventured up there with my camera… but you will be first to know when I do!

It is the pitot tube for the air speed indicator.

John.

Sorry, John, for a slight correction.

It is a ‘pressure head’, which accepts both pitot and static pressure.

I bench-checked them at Boscombe Down.

Bri 🙂

Nice to see so many people taking an interest in them at last.

Its is yeh :rolleyes:

Come a see our two live one’s at Brunty 😉

Nice to see so many people taking an interest in them at last.

I too am really starting to like the lightning, I think its a combination of its shape and that intake, And the more i have looked into them, the more I am amazed, Id have never thought they had such a long service career…Thanks for the info fella’s 😉