View Full Version : Para Visual Display on the 744 (PVD).
MATMAX
31st Jul 2009, 16:37
Hi Guys,
Does someone can give me some info about this system ?
Saw it de-activated in a 744 from a well-known very safe airline.
Any pic please ?
Merci.
TopBunk
31st Jul 2009, 17:51
Briefly, without referring to notes!
1. Tune in the ILS for the departure runway (freq and qdm)
2. Both Capt and FO select PVD on (switch to left/right - for capt/fo) on upperside of coaming
3. Adjust brightness as required
4. When within x (80deg?) of centreline, it displays as a barbers pole
5. In general, during the t/off roll, it will indicate which way to steer according to streaming barbers pole - it is very intuitive.
6. After t/off the displays blanks/shutters
The PVD was developed by Smiths Industries in the UK around 1961.
The original intention was to have one vertically and one horizontally mounted barbers pole in the pilot’s peripheral vision to provide guidance during approach and landing. This configuration was not very effective, I'm not sure if any aircraft actually used it in service.
It was used on Trident aircraft, only utilising the horizontal pole mounted in the glareshield for guidance on the runway, I seem to recall that it was driven by its own separate computer; so most likely a CAA requirement for Cat 3 landings at that time.
I have not been able to locate any pictures.
QA1
leewan
31st Jul 2009, 19:47
http://www.asc.gov.tw/downfile/SQ006_ENG.pdf
Go to page 159 of this report. (It's page 182 on the Adobe reader.)
You will get everything you need to know about the PVD.:)
jimpy1979uk
31st Jul 2009, 19:55
No pictures but the system works as follows,
The signal required is the Localiser which is fed to the PVDs. It is used primarilly for roll out control of the aircraft. Any deviation from the centre line is fed to the PVD which makes the barbers pole rotate in such a way that it makes you feel like the aircraft is moving off the centre line. When the deviation is corrected the barbers pole once again stops moving.
A good way of experiencing a similar feeling is to sit on the flight deck on an aircraft outside a hangar and the hangar doors are being opened. Concentrate on the flight deck instruments and the movement of the hangar doors in your parapherial vison will make the aircraft seem like its moving.
MATMAX
1st Aug 2009, 07:15
Merci Gents.
Now I understand why "barber pole" (even if there is none in France ...).
Thanks Leewan ...
Salut.
MATMAX
1st Aug 2009, 07:23
Why it has been de-activated if it was so reliable ? (useless ?).
leewan
1st Aug 2009, 10:21
Why it has been de-activated if it was so reliable ? (useless ?).
I think it has got to do with the fact that when this was manufactured in the 60s, there were no electrical PFDs and NDs that could identify the runway electrically and this was the only equipment that could at that time. Now, there is the PFD, ND and the EFB's rotating airport map layout that could confirm your a/cs runway and it's orientation to it, causing it to become obsolete.
MATMAX
1st Aug 2009, 21:25
OK Tks Leewan,
but i know the EFB on the 777 only ...and a test on a 345 ...
All our 744's have a PVD except perhaps, two or three aircraft we purchased second-hand from other airlines (these airlines had already deactivated them or never had them fitted).
They are fitted to some 747-400ER's, so they are obviously still in production
Whilst the primary reference is the localiser signal, the PVD's need the Inertial Reference System to compute lateral (sideways) acceleration.
I don't know how intuitive they are, but you steer the aircraft in the direction the display appears to be moving towards.
Rgds.
NSEU
The original intention was to have one vertically and one horizontally mounted barbers pole in the pilot’s peripheral vision to provide guidance during approach and landing. This configuration was not very effective, I'm not sure if any aircraft actually used it in service.
AFAIK, there was only one civil aircraft that had this capability, and in fact only one particular model...the Grumman Gulfstream One, and that aircraft was owned by the US television and radio personality, Arthur Godfrey.
This aircraft was FAA approved, at the time, for CATIII hand flown approaches.
PVD...very effective, if used properly.
MATMAX
2nd Aug 2009, 08:48
Gents , thank you for your answers and explanations.
The a/c , I have worked on is an ex-SQ (ex-SPB) , thats the reason why Mr Leewan knows about it .
It was the first time that I saw this system , anyway I worked only on the 744 from AF , AC , TG , JL , NH , KE and BR and none of them get it (as far as I can remember...).
Happy to see that even after 20 years experience , I am still discovering new things (from the 60s) ...(who is laughing ?).
Merci.
NightDog83
12th Sep 2010, 07:53
Greetings
The posted link for the file .pdf would not open. Can someone post a better link?
I had a question for anyone with experience with PVD if there was any indication if there was a latent failure in the guidance or if the system was invalid?
Off Flag? Color change? etc.,?
How would the pilot "know" guidance was valid?
Thanks
Nightdog83
spannersatcx
12th Sep 2010, 08:07
go to the link, remove the last bits of the url, so you're at the .gov.tw bit click on english, then downloads, then the file, it's not difficult!
NightDog83
13th Sep 2010, 05:43
OK, From reading the document, it looks like when it is functioning as intended, the PVD is "unshuttered"
In a more modern glass cockpit, I would make the analogy that the indication would be displayed for view when valid and removed from view when not valid. Kind of like how some Flight Directors are biased out of view when invalid.
For any on the forum who have experience with the PVD, is this a reasonable analogy?
Thanks
Nightdog83