Tornado Down Part 2
Join Date: May 2004
Location: Granada, Spain
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Fox four...bit belated but...and apologies for any thread drift...
I was the resident 43Sqdn A shift radio guy in those heady days...
Turns out the problem wasn't unique to XV571 but was common to all FG1 a/c and the reasons behind it only came to life much later. The lower UHF antenna was located on the forward facing nosewheel door on the opposite side of the door to the Nosewheel steering motor.
In 1981, during EMC testing of the then new PTR1751 radios on the FG1 Phantom it was found that transmissions on a couple of quite narrow bands of frequencies from the lower UHF antenna regularly caused steering shimmy when stationary or steering deviation when moving during taxying, take-off or landing. (Strangely enough I left the RAF in 79 and in 1980 joined Plessey's ASR889 Installation and Development team and one of my first tasks was EMC testing the PTR1751 on the FG1; what goes around comes around...)
Needless to say, Leuchars Tower UHF frequency at the time just happened to coincide with one of the affected bands of frequencies. The immediate solution was to include an instruction to the crews that transmissions on the ground should only be made using the upper UHF antenna located in the fincap, just as far away from the NWS as possible.
Prior to fleet fit of the new PTR1751 radios, it was fairly uncommon to find an old PTR374 that would produce the necessary Tx power to cause the upset, but just occasionally one would get a good one...anything in excess of 17W would do it...and the PTR1751 was good for 25W normally.
Another little aside concerning XV571; it was 43 Sqdn's bosses mount and I lost count of the number of times he reported loss of comm during 4G+ port turns. That particular aircraft had crap PTR374 mounting tray rear connector mounting springs and despite the T/R being hammered home into the mounting tray and the thumbscrews tightened as much as possible there was always a degree of float so that in a hard port turn, contact would occasionally be lost between the T/R and the tray connector. Repairs to the rear connector were nigh on impossible so during a engineering debrief I jokingly suggested to the boss that perhaps he should restrict his turns to +3.5G or less. He found the remark highly amusing and complained that that would take all the fun out of chasing away Ivan, but S.Eng.O thought otherwise...
Shortly thereafter BAe Brough and the Flight Test Centre at H-O-S-M detected excess fatigue in the wing fold hinges and imposed a +3.5G limit anyway...
pp
edited to remove a couple of 'oops' senior moments
As this is a 'rumour' forum, might I suggest NWS fault? XV571 did a similar thing at Leuchars circa 77? Metal in the follow up potentiometer I believe, and I think the future 43 sqn boss was in the back?
Turns out the problem wasn't unique to XV571 but was common to all FG1 a/c and the reasons behind it only came to life much later. The lower UHF antenna was located on the forward facing nosewheel door on the opposite side of the door to the Nosewheel steering motor.
In 1981, during EMC testing of the then new PTR1751 radios on the FG1 Phantom it was found that transmissions on a couple of quite narrow bands of frequencies from the lower UHF antenna regularly caused steering shimmy when stationary or steering deviation when moving during taxying, take-off or landing. (Strangely enough I left the RAF in 79 and in 1980 joined Plessey's ASR889 Installation and Development team and one of my first tasks was EMC testing the PTR1751 on the FG1; what goes around comes around...)
Needless to say, Leuchars Tower UHF frequency at the time just happened to coincide with one of the affected bands of frequencies. The immediate solution was to include an instruction to the crews that transmissions on the ground should only be made using the upper UHF antenna located in the fincap, just as far away from the NWS as possible.
Prior to fleet fit of the new PTR1751 radios, it was fairly uncommon to find an old PTR374 that would produce the necessary Tx power to cause the upset, but just occasionally one would get a good one...anything in excess of 17W would do it...and the PTR1751 was good for 25W normally.
Another little aside concerning XV571; it was 43 Sqdn's bosses mount and I lost count of the number of times he reported loss of comm during 4G+ port turns. That particular aircraft had crap PTR374 mounting tray rear connector mounting springs and despite the T/R being hammered home into the mounting tray and the thumbscrews tightened as much as possible there was always a degree of float so that in a hard port turn, contact would occasionally be lost between the T/R and the tray connector. Repairs to the rear connector were nigh on impossible so during a engineering debrief I jokingly suggested to the boss that perhaps he should restrict his turns to +3.5G or less. He found the remark highly amusing and complained that that would take all the fun out of chasing away Ivan, but S.Eng.O thought otherwise...
Shortly thereafter BAe Brough and the Flight Test Centre at H-O-S-M detected excess fatigue in the wing fold hinges and imposed a +3.5G limit anyway...
pp
edited to remove a couple of 'oops' senior moments
Last edited by Phalconphixer; 15th Feb 2011 at 17:23.
Join Date: Sep 2002
Location: London
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VC10 Aeromed
Happy to be on the crew of the 40+ y/o funbus sent to God's own country to collect the crew of the 25+y/o electric jet and drop them off dahn Saff. Sadly bad weather meant they ended up in RAF Oxfordshire rather than Birmingham, but we tried our best.
Hope they're both recovering nicely and coping with their temporary height loss...
Hope they're both recovering nicely and coping with their temporary height loss...
. Out of interest, how long did it take you to generate the sortie and make the trip up north?
