Fixing an F-105 , 1960s, by Dave Gurtner
From MemoryArchive
Who: Dave Gurtner What: F-105 Where: Unclear When: 1960s?
F-105D-20-RE 61-0150 ("Dollar-Fifty") had a problem -- a weird problem -- "red diagonal" write-ups (not safety of flight glitches) on each of its last three sorties. Each pilot reported a "thumping noise" during climb through 30,000 feet at subsonic IAS. 150's stand-in crew chief, A1C Rayburn Wood ("Woodie," of course), sat chain-smoking in the 23rd TFS flight shack researching the Republic Aircraft "Dash 2" maintenance manual and the troubleshooting charts. Being the recent A1C promotee that I was, I figgered I'd dazzle Woodie with my brilliance: "Hey, Woodie, can I bum a smoke from ya? Thanks. Oh, by the way you ever hear of this "duck buzz" thing?" (BTHOOM where I had ever heard of such a thing, or how I had turned it into some sort of "duck sound!" Anyway, it has dawned on me in my advanced years that it's probably impossible to encounter real "duct buzz" at subsonic airspeeds...)
Woodie immediately turns to the variable air inlet (VAI) test procedures: "Bad news. Sez we gotta jack the bird up [this gets the main LG microswitches open], then apply electric power and hydraulic pressure, and press this little rubber-covered button next to the auxiliary air intake in the left main wheel well. I've noticed it before on preflights, but never knew what it was for... Oh yeah, we also gotta manually hold those aux intake doors in both wheel wells shut during the test."
Based on my wise-assed remark, this was shaping up into the ultimate daytime nightmare for any Thud crew chief -- not only manhandle three 20-ton jacks under the beast and pump away on 'em for about half an hour to get it up off the ground and level (verrrrry aerobic, by the way), but then hook up an MD-3 and that damn 2-ton MJ-5 hydraulic "mule" -- ahhh, you always got to experience that warm hydraulic fluid dribbling down your upraised arms into your armpits while struggling with the supply and return hose connects on the aircraft!!! BTW those external hydraulic power connects, and everything else on the Thud-- already "tall" for the ground maintenance types -- all get taller by over 2 more feet when the bird is up on jacks.... even the cockpit boarding ladder gets a longer first step up!!
A sweaty hour later, the MD-3 and MJ-5 are roaring away at over 1500 RPM, that red juice is stabilized at 200 degrees/2800 PSI, the juice pools at the lowest point of the hose arcs are minimal in the drip pans, roll-around stands are under each main wheel well, extra manpower has been recruited, and other Thud chiefs are stopping by to find out what the heck all the commotion's about. Woodie steps up on the L/H stand (next to the A2C holding shut the aux inlet door on that side) and elegantly presses that rubber-covered button way up there in the wheel well.
Well, the book sez this is what's supposed to happen: the screwshaft-driven plugs in each air intake should slowly whine forward and then aft (electric motor noises, as the plugs vary the air intake geometry) and then the pair of hydraulically-driven air "dump" doors on each side of the fuselage open and then sloooowly shut (that shows they're ready to dump excess pressurized air from the mid-inlet, if necessary, just ahead of that J75's voracious compressor section). Well, 150's intake plugs do their thing OK, but there's no action at all on the air dump doors and a great "thumping" sound is resonating all over the airplane!!! I mean, you could have heard the noise from 20 feet away if not for all the exhaust noise from the power carts!! Anyway, the guy in the cockpit is feeling the "thumps" in his butt -- closer inspection (using a unique "palm of hand" technique 'cuz of the cart noise) shows the "thumps" are originating from somewhere under the ejection seat.
...And now for the rest of the story: A component that Republic Farmingdale said would NEVER fail DID -- it was a four-way hydraulic pressure switching valve located in just about the godawfullest place possible on a Thud: not up in the "hell hole" (true Thud chiefs know this place intimately) but under the cockpit floorboards! Woodie had a long, long, night ahead -- get the beast down offa the jacks and into the hangar, get the canopy off and seat out, and remove the cockpit side consoles and floorboard to get access to that stupid "non-fail" valve. Then, reverse all this disassembly work after replacing the valve -- and schedule a full safety check flight for 61-0150 after a week or so of "hangar queendom," fighting off all those damn "cannonball" part orders (cannibalization of parts for other wing Thuds 'cuz all the good stuff is going to SEA for the Thuds there...).
I don't recall Woodie ever again taking seriously anything I said -- on any subject at all...
Co-opted from Personal Recollections and War Stories
