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Aerodynamic Unporting

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Aerodynamic Unporting

Old 22nd Dec 2005, 14:13
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Question Aerodynamic Unporting

Hi All

Read in E.K. Gann's Fate is the hunter about "Aerodynamic Unporting". This aparrently occured on some early models of the DC-4, due to some failure in the horizontal stabilizer coupled with certain CofG possitions. I understand unporting in fueltanks and oilsumps...but could someone please expain the aerodynamic version of this to my primitive brain.

Thanx

Rabid
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Old 22nd Dec 2005, 17:59
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Never heard of it.

I've got a little time in the DC6 so I'd be interested to read about this.

Little ashamed to admit I've never read Fate is the Hunter...

I know, I know...

Maybe you can use the phrase in a sentence and put it in context for us less-than-well-read ones.
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Old 24th Dec 2005, 06:53
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Happens to me when I drink a lot of beer.
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Old 24th Dec 2005, 07:20
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Was this when venting fuel from full tanks ran along the underside of the fuselage and into an intake with electrics nearby? I think this brought down several DC-4's. There was also a Constellation that dumped fuel in a holding pattern, flew into its own vapour which brought that down too.
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Old 24th Dec 2005, 07:40
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Cabin heater fires on the DC6

Standby Scum--The DC6s were grounded briefly after a couple uncontrollable fires caused by fuel venting into the cabin heater intake.

But I'm still very interested to hear about the DC4 and its problems with CG and the horiz stab...

...sounds like an entirely different situation.
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Old 24th Dec 2005, 23:18
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I vaguely recall reading some where in the dim dark past that it had some thing to do with a bolt coming out of an elevator hinge. Seem to recall that an interviewer asked Gann the question. Memory being what it is I could be up a creek without a paddle.
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Old 25th Dec 2005, 08:09
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Ernie Gann's fate

I recall from the book "Fate is the hunter" that Gann was recounting an incident of unusual vibration on a DC-4 about midway (of course!) between Hawaii and California. Since he was to begin his vacation upon completion of this trip and they were "fat" with fuel, he cancelled all power reductions and completed this flight and the final leg from BUR to OAK at max cruise power. Another DC-4 went into an uncommanded dive and crashed less than 24 hours later. The entire event was witnessed by senior pilots and the chief of the accident investigation division aboard a Civil Aeronautics Board aircraft flying 3 miles away. Gann filed a report on the vibration and went on a 3 week sailing trip. Upon his return, he was contacted by an engineer named "Howard", who explained that the entire DC-4 fleet had been grounded because of his report and the loss of the other DC-4. "Unporting" was an issue said to be related to the mass balance properties of the elevator. A missing hinge bolt would tend to facilitate the phenomenon. Howard claimed that Gann flew his plane at the only combinations of weight, balance and speed that would prevent "unporting" and the subsequent loss of elevator effectiveness and pitch control. In essence, Gann's rush to start his vacation saved the day!

No theoretical details were provided in the book.

Best regards,

Westhawk
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Old 25th Dec 2005, 19:38
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"Howard" in this case was Ben O. "Benny" Howard, who was Donald Douglas' chief test pilot. He flew the first flights of the "DC-4E" (look that one up on Google), the A-26, DC-6 and others. He previously was a senior UAL pilot, and worked closely with Douglas on the design of the P&W R-1830 installation in the DC-3 for UAL. After semi-retiring from Douglas he developed the "Howard Maximizer" speed kit for the DC-3.

But all this was after his outstanding career as a race plane designer/builder pilot. His DGA-6 won all the big money in 1935.
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Old 26th Dec 2005, 08:33
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The DC-4 problems referred to were the result of a generally underdesigned elevator hinge arrangement, and were solved by redesign.
On the DC-6, this also, oddly enough, re-appeared, and the 'fix' was to add an additional elevator hinge at the extreme tip, to aleveate unwanted vibrartion, which manifested itself as a rather unpleasant control surface flutter at Vne.

The DC4, DC6 and the DC7 shared the same wing planform (with minor variations, mostly washout toward the tip) but had entirely different tail surface arrangements, with regard to Reynolds number.
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Old 26th Dec 2005, 23:59
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Was forced to get Ganns book out to prove the memory chips have not over dosed on UV. The problem was due to the bolt coming out of the left outboard elevator hinge. Howards explanation in the book says 'Unporting is the balance destruction of the elevators by aerodynamic force. ----- if enough seperation between the fixed and balance portion of your elevator occurs, your airplane will go into a vertical dive -----' My take is they are talking of the onset of flutter bought about by the outer one third of the elevator span being unsupported - which is where the issue of speed and C of G would enter (lift demanded of the elevator). Any aerodynamisists out there?
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Old 27th Dec 2005, 06:46
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Barit1:

Thanks for the info on the identity of "Howard". Since the first time I read Gann's epic tome, I have wondered if this was the Howard of the DGA series aircraft fame or perhaps related to the Dee Howard company, notable for their many aircraft modifications and bizjet thrust reversers, among other things.

Best regards,

Westhawk
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Old 27th Dec 2005, 12:41
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No connection between Benny Howard and Dee, except that Benny was born in Texas (Palestine), and Dee's shop is in San Antonio.

Benny died in 1970, and his eulogy was given by Donald Douglas.

Last edited by barit1; 31st Dec 2005 at 00:51.
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