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Interviews with D P Davies on certificating aircraft

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Interviews with D P Davies on certificating aircraft

Old 21st Dec 2017, 08:53
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Originally Posted by LeadSled
Folks,
At the risk of a bit of controversy, and having flown B707-300 and -320 modified as required to be UK registered, (total about 8000 h on various versions, on various registers) versus the FAA certified aeroplane, it is my opinion that the ARB required mods. were overall detrimental to the operation of the aircraft.
Excerpt from Tex Johnston 'Jet age Test Pilot'

During the second flight of the Dash80 we ran into rough air while doing stability and control work at 2,000ft ,gear and flaps down,speed below 200mph.Again I noted the Significant tendancy to Dutch Roll.In my test report I recommended additional attention to directional stability.
Directional stability was eventually improved by using the ventral fin and/or larger Fin (vert stabilizer).But it is clear even from the Dash 80 2nd flight that directional stability was marginal at best - Johnston had hoped that good training would suffice but he did realise after the Braniff 707 training accident (plus his own observations with other airlines problems) that aircraft modifications were essential and he did not pull any punches with Boeing about the subject.

From a safety point of view it had become clear that directional stability improvements were essential for the 707 so not sure how that could be detrimental ?
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Old 21st Dec 2017, 10:30
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Originally Posted by LeadSled
Folks,
At the risk of a bit of controversy, and having flown B707-300 and -320 modified as required to be UK registered, (total about 8000 h on various versions, on various registers) versus the FAA certified aeroplane, it is my opinion that the ARB required mods. were overall detrimental to the operation of the aircraft.
I think we all acknowledge the B707 (and DC-8) had shortcomings, and aircraft design advanced by leaps and bounds over the period in question, '50s through the -80s, but the demanded changes for the B707 were, as far as I am concerned, largely a safety minus.
We should also acknowledge that aircraft certification standards have made great strides since the original SFAR 422b.
Tootle pip!!
The "ARB" modifications were applied to all extant 707s at the time. I would like to know when you think that you have flown a 707 without these mods (it would have to have been over 55 years ago). How improved directional stability, full rudder boost and elimination of the possibility of ground stalling can be detrimental escapes me.
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Old 21st Dec 2017, 12:39
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IIRC the 707-436 had a parallel yaw damper which had to be disengaged for take-off and landing and even with the extra fin area (main + ventral) their was a continuous mild tendency to dutch roll. This was not the case with the -321C which had a series yaw damper and thus no ventral fin. It would have been interesting to hear DPD's opinion of the stab trim motor stalling under large mistrimmed conditions.
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Old 21st Dec 2017, 13:09
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Originally Posted by Meikleour
IIRC the 707-436 had a parallel yaw damper which had to be disengaged for take-off and landing and even with the extra fin area (main + ventral) their was a continuous mild tendency to dutch roll. This was not the case with the -321C which had a series yaw damper and thus no ventral fin. It would have been interesting to hear DPD's opinion of the stab trim motor stalling under large mistrimmed conditions.
The ventral fin was to prevent ground stalling through over rotation. The -320C had three section leading edge flaps which altered the lift distribution and allowed the elimination of the ventral fin. Early -320Bs had the ventral fin, but the -320C wing mods were applied to this variant and it was eliminated. Some at least of the early -320Bs were modified to the later spec (including the VC-137C 62-6000). The 707-436 was mechanically and aerodynamically the same as all -320 and -420 variants, the only difference being that the -420 had Conways instead of JT4As.
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Old 21st Dec 2017, 14:34
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Alan Baker: thanks for those details. Twas a long time ago!
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Old 6th Jan 2018, 08:21
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I am resurrecting this post in the hope that some readers may have an interesting story or two to tell about stalling large aircraft. For example have anyof you ever spun a large four engine transport?
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Old 6th Jan 2018, 08:42
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Originally Posted by Bergerie1
I am resurrecting this post in the hope that some readers may have an interesting story or two to tell about stalling large aircraft. For example have anyof you ever spun a large four engine transport?
I've experienced a stall in a Viscount (with no passengers on board, I hasten to add). It was pretty benign.

A spin would have been interesting.
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Old 6th Jan 2018, 14:07
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It was rumoured that Ron Gilman took a Vanguard beyond the buffet on a base training detail which caused it to invert. The resulting high airspeed on the recovery led to a twist in the fuselage - or at least that is the story I was given to explain why that particular aircraft was almost impossible to trim properly!

Last edited by Meikleour; 6th Jan 2018 at 16:16. Reason: withdrawing info
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Old 6th Jan 2018, 23:38
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For example have any of you ever spun a large four engine transport?
Not me and not four engines. Guys seem unflappable.

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Old 12th Jan 2018, 06:48
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Two brief statements were made that I
would be curious if anyone can elaborate on


He mentions the DC8 once in passing but
not again ?

He refers to the HS748 as a ‘heap’


Can anyone add to and / or clarify?
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Old 12th Jan 2018, 09:22
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I am resurrecting this post in the hope that some readers may have an interesting story or two to tell about stalling large aircraft
On 3/8/83 I was the FO on an air test on B747-136 G-AWNB. We got permission to enter the Portland danger area where we carried out a full stall. Apart from the rather large height loss, the stall was easily recoverable, with no wing drop. However the intense buffeting was most uncomfortable. It was totally impossible to read the instruments. I felt sorry for the engineer on the jump seat trying to read the IAS.

Fortunately, shortly afterwards, the CAA removed the requirement for a full stall on air tests.
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Old 12th Jan 2018, 14:02
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A couple of reports on stalling the DC-10.

Report: Fedex DC10 near Raymond on Jun 14th 2008, aerodynamic stall while in holding

https://www.ntsb.gov/investigations/...ts/AAR8010.pdf
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Old 13th Jan 2018, 10:20
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Back in the 1970s there was a stall incident on a Standard VC10 during a CofA airtest. The Standard VC10 had wing fences on both the wing and the leading edge slats such that when the slats were retracted they abutted to form one continuous fence on each wing. In the clean configuration air leakages outwards along the span were prevented by rubber blocks.

On the flight in question, I can't remember now whether the blocks on one side were missing or merely damaged, however, when they came to do the clean stall the air leakage through the gap was sufficient to make that wing stall before the other. The wing dropped and they went beyond 90degs of bank before recovering. This would have been up at somewhere between 15,000 and 20,000ft.

They recovered the aircraft without damage and it was only afterwards that the missing/damaged blocks were found. After that, one of the checks before a test flight was always to inspect these blocks.

One lives and learns!!
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Old 13th Jan 2018, 21:16
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And thanks for reminding me that I still needed to add that story to my site! See here: Incidents and Accidents
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Old 27th Jan 2018, 19:14
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The Viscount stall/spin story - bloody hell - I had no idea!
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Old 29th Jan 2018, 17:22
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Actually, though I enjoyed listening and have some respect for the man, I do resent his 'a 16 year old boy could fly it' comments about 747 and Concorde. No doubt a sarcastic comment which he didn't expect anyone to take seriously, but our profession really could do without being undermined in that way.
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Old 29th Jan 2018, 17:33
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I think he was comparing it to earlier aeroplanes - and TBH 16 -18 year olds have flown some very advanced fighters...............................
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Old 29th Jan 2018, 17:54
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[QUOTE= - and TBH 16 -18 year olds have flown some very advanced fighters...............................[/QUOTE]

Certainly, and bombers as well, but I recall he said something like 'any 16 year old who can ride a motorbike could get it around the circuit'. Which is bull**** and anyone with substantial experience as a flying instructor and a training captain would know it.
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Old 30th Jan 2018, 00:34
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ZeBedie, I'll bet Thomas Dobney could.

Post #22

2i/c with only 279 hours - all on type. What gives..
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Old 30th Jan 2018, 05:23
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Well - I took a bunch of 12/13 year old school boys and their headmaster onto a 747-200 simulator many years ago for an end of term treat. I found most of them could not fly it (including the headmaster) without a considerable amount of help from me. However, two did remarkably well, needing only a few verbal prompts. I was very surprised how well they did. But the headmaster was not much amused!
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