Test Pilots - The Good, the Bad and the Ugly!

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Test Pilots - The Good, the Bad and the Ugly!

#1 Post by Cacophonix » Tue Jun 19, 2018 9:36 am

Following on from my interest in the design, testing and history of the Pegasus engine and the Harrier I was apt to look at some of the pilots who tested some of the historical types that were (and may still be) at the cutting edge of technology (or not) and whose flying attributes may have been a black box to the men and women who flew them from the outset.

Their formidable skills, both technical and piloting, coupled with the ability to communicate with and influence, often recalcitrant management, is hugely impressive to me and thus in order to bring some of their lights out from under their bushels or, sadly, their gravestones I have started this thread.

What other pilots and technicians or mere mortals would ops-normalisers add to this list. Electing to mention oneself is to be encouraged and even test flying a home built light aircraft or even a self designed and built balsa model would make for interesting reading! Don't be shy, I can think of a number of flights in well know and simple types that have become trials and bona fide test flights after maintenance and the like. Let it all out, you know you will feel better for it! ;)))

The first person I have chosen fits into the gravestone category unfortunately but he definitely fits the good test pilot characterisation having worked for Hunting Aviation (amongst other very well know companies) and was an integral part of the team that tested the successful Jet Provost Trainer. Sadly he was killed when the testing the Jet Provost T.Mk.4 just as the aircraft was coming into production for the RAF and other air forces all over the world.
Lt Cdr J. R. S. Overbury.JPG
Lt Cdr J. R. S. Overbury.JPG (17.05 KiB) Viewed 1014 times
Lieut-Cdr J.R.S.Overbury served in the Royal Navy from 1943.,being granted a permanent commission in 1950.. He served with No 816 and 810 Squadrons (HMS Ocean and Theseus). He took the CFS course in 1950 and was a graduate of No.12 Course ETPS at Farnborough 1953. He was on Naval Test Squadron A and AEE between 1954-1956. He set several record, as listed below.

Flying a Sea Hawk F.B.3 from Bovingdon to Schiphol he set a new point-to-point record in Class C.1 from London to Amsterdam. He flew the 224miles in 23min 39.7sec at a speed of 571.5mph. on the 29th July 1954. Another point-to-point record was set on the 2nd July 1955 between Ciampino, Rome and Luqa, Malta. Lieut-Cdr J.R.S.Overbury with Lieut-Cdr G Kable as navigator flew a Royal Australian Navy Sea Venom F(A.W).53 the 422 miles in 47min 24sec at a speed of 538mph.

He joined Saunders Roe as a test pilot in 1957 and joined Hunting Aircraft at Luton as a test pilot in 1959. On 16th November 1960 he was killed whilst flying Jet Provost T.2 G-AOUS. The aircraft disintegrated over Langford, 3 miles south of Biggleswade, Beds.
https://thetartanterror.blogspot.com/20 ... -1960.html

Hunting Jet Provost

Tragedy struck the programme on 16 November 1960, when G-AOUS, piloted by Lt Cdr J.R.S. Overbury, a Hunting test pilot since 1957, took off from Luton on airspeed trials. The aircraft was recovering from a dive at the maximum design speed, when the positive G encountered forced the nose leg to descend into the airflow. The leg and both nose undercarriage doors were promptly ripped off, forcing the aircraft to violently pitch, nose upward. The rapid change in attitude caused both wings to detach and the fuselage to break-up. The pilot was killed. An obituary appeared in Flight on 25 November 1960. Jack Overbury It is with regret that we record that Lt Cdr J. R. S. Overbury lost his life on Wednesday of last week in an accident to a Jet Provost which he was test flying. Jack Overbury joined Hunting Aircraft from Saunders Roe Ltd, where as chief test pilot he had concluded the SR.53 prototype trials, in March last year. In 1954 he was awarded the de Havilland Trophy for a point-to-point London - Amsterdam record (at 571.5 m.p.h.) he set up in a Sea Hawk; and in 1955 he established a Rome - Malta record in a Sea Venom at a speed of 538 m.p.h. He had a serious accident at Sandown, IoW, in 1958 while demonstrating a Druine Turbulent. His injuries necessitated four operations and he was grounded for several months, only his determination to fly again bringing him back into the test pilot’s profession.
Jet Provost, The Little Plane with the Big History – Bob Clarke



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Re: Test Pilots - The Good, the Bad and the Ugly!

#2 Post by Cacophonix » Tue Jun 19, 2018 2:27 pm

Apropos the Provost I was stunned to be talking to better half today when the distant sound of a Viper engine assailed our ears and, without looking up she said, sounds like a Jet Provost to me, and lo and behold one of the resident North Weald Provosts hove into view. I was most impressed!

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Re: Test Pilots - The Good, the Bad and the Ugly!

#3 Post by boing » Tue Jun 19, 2018 3:24 pm

The JP had an unusual landing gear design with one main hydraulic cylinder positively connected to all three gear legs by a system of chains and sprockets. I can well imagine that the nose wheel being forced down at very high speed would result in all sorts of havoc being transmitted to the rest of the gear system and quite possibly the nearby flight control cables also.

I was flying a brand new Mk4 (11 hours on the clock) when the undercarriage failed to lower correctly due to lack of locking wire on the end of the hydraulic cylinder rod. Following the check list action of recycling the gear just made the situation worse since every time I cycled the gear the connection to the hydraulic cylinder rod unscrewed a little more resulting in more gear legs not locking down. After being assured by close airborne inspection that the gear lights were false indications I attempted to land with three red gear lights illuminated and of course the legs started to fold up on touchdown. Luckily the touchdown caused one main leg to go onto the locks and, since the nose gear extends rearwards, that too was forced onto the locks by ground contact leaving only the left main gear to actually collapse. Since I had an engineering officer in the other seat on an air experience ride I bet he got some good stories for the troops from our adventure.

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Re: Test Pilots - The Good, the Bad and the Ugly!

#4 Post by Cacophonix » Tue Jun 19, 2018 4:16 pm

boing wrote:
Tue Jun 19, 2018 3:24 pm
The JP had an unusual landing gear design with one main hydraulic cylinder positively connected to all three gear legs by a system of chains and sprockets. I can well imagine that the nose wheel being forced down at very high speed would result in all sorts of havoc being transmitted to the rest of the gear system and quite possibly the nearby flight control cables also.

I was flying a brand new Mk4 (11 hours on the clock) when the undercarriage failed to lower correctly due to lack of locking wire on the end of the hydraulic cylinder rod. Following the check list action of recycling the gear just made the situation worse since every time I cycled the gear the connection to the hydraulic cylinder rod unscrewed a little more resulting in more gear legs not locking down. After being assured by close airborne inspection that the gear lights were false indications I attempted to land with three red gear lights illuminated and of course the legs started to fold up on touchdown. Luckily the touchdown caused one main leg to go onto the locks and, since the nose gear extends rearwards, that too was forced onto the locks by ground contact leaving only the left main gear to actually collapse. Since I had an engineering officer in the other seat on an air experience ride I bet he got some good stories for the troops from our adventure.

.
The original Provost prototype's undercarriage appears to have been a most Heath Robinson affair and it is interesting to read that even after the system had been completely overhauled, redeveloped and lowered by some 22 inches, by the time the Mk4 came along, it was still possible for manufacturing errors/maintenance errors to cause undercarriage problems.

The original concept relied up the use of the Percival Provost as the basis for the prototype (as all who post here will know)…
Percival Provost.JPG
Percival Provost.JPG (39.59 KiB) Viewed 980 times
The Viper was mounted in the old cockpit, forward of the original rear bulkhead and above the main spar. Two large engine doors and a removable central beam took the place of the transparencies. The cockpit was moved forward with the rear bulkhead now aligned with the mainplane leading edge. This was, in turn, fitted with a streamline nose to house the battery, radios, and instrumentation; later this would include oxygen bottles as well. The two intakes were fitted to the sides of the cockpit structure, forward of the wing leading edge. Moving the cockpit forward, just over three feet and moving the heavy engine to a more central position entirely changed the aircraft’s centre of gravity. Luckily, with no propeller in the way less ground clearance was required, and consequently the tail wheel was substituted for The problem was that the span of the propeller had dictated the length of the main undercarriage, and as the object of the exercise was to keep cost to a minimum, it was cheaper to fit a nose leg that complimented the existing mains, rather than completely redesign the system. Eventually a shock strut with the correct extension was located; bizarrely it was actually a slightly modified Bristol Sycamore leg. The consequent tricycle arrangement meant that the only way to access the aircraft cockpit was via a set of ‘A’ frame steps. The undercarriage arrangement also gave rise to some interesting taxiing characteristics, especially on grass, as the aircraft crabbed and wandered around alarmingly.
Jet Provost, The Little Plane with the Big History – Bob Clarke
XD674.JPG
XD674.JPG (38.85 KiB) Viewed 988 times
and then...
Provost T.Mk.1..JPG
Provost T.Mk.1..JPG (29.37 KiB) Viewed 988 times
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Re: Test Pilots - The Good, the Bad and the Ugly!

#5 Post by Fox3WheresMyBanana » Wed Jun 20, 2018 3:35 pm

The JP undercarriage caused me to put out my only Mayday, when shortly after T/O on an early solo ccts trip I experienced heavy airframe vibration and a hammering noise just like a compressor stall. After a climb and precautionary glide circuit to land, it was discovered that both the nosewheel leg and nosewheel doors were out of adjustment, causing the still revolving nosewheel to bang against the inside of the doors. The spinning wheel would bash the doors open a bit, whereupon the airflow would close them, and repeat rapidly. The wheel ran out of energy at about the same time I pulled the power back on reaching a safe glide height. Non-JP pilots should note the engine, like the nosewheel, is just behind and below the pilot(s) (most of the JP fuselage contains a long jetpipe).

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Re: Test Pilots - The Good, the Bad and the Ugly!

#6 Post by Ex-Ascot » Thu Jun 21, 2018 7:23 am

Sounds that I was lucky with the thing then.
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Re: Test Pilots - The Good, the Bad and the Ugly!

#7 Post by boing » Thu Jun 21, 2018 7:26 pm

As a pilot you inevitably field questions from the non-involved about technicalities, often such as "Why did they do something this or that way? What is this piece for?". My oft spoken comment is that all aircraft are a compromise between good handling which the pilot would like, simple design which the engineer would like, low cost which the beancounters would like and visual appearance which the sales department would like. The Jet Provost suffered from this compromise in spade fulls.

The basic idea of using a piston airframe as a basis for the design of a jet was suspect from the start but the beancounters, I am sure, loved the idea. "Think how much money we will save" ..... right!! We need a jet engine that will fit, why not use the one we use in the Jindivik? We can save money that way. Actually worked out to be a good choice. Don't bother to redesign any systems ....... wrong.

After all this compromise the people that made the project work were principled test pilots such as Lt Cdr Overbury. These are the people that took that bag of nails and said that this is acceptable, this is not acceptable, why don't we try this idea? These are the people that, in pre-computer days, stuck their neck out (and sometimes paid) and gave us aircraft that, whilst not being perfect, we knew about their faults and we could trust that if we stayed within the limits defined by the test pilots we would have no problems. We also knew clearly what we could expect if we had to operationally slide over the limits.

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Re: Test Pilots - The Good, the Bad and the Ugly!

#8 Post by Cacophonix » Sat Jun 23, 2018 8:12 am

boing wrote:
Thu Jun 21, 2018 7:26 pm
As a pilot you inevitably field questions from the non-involved about technicalities, often such as "Why did they do something this or that way? What is this piece for?". My oft spoken comment is that all aircraft are a compromise between good handling which the pilot would like, simple design which the engineer would like, low cost which the beancounters would like and visual appearance which the sales department would like. The Jet Provost suffered from this compromise in spade fulls.

The basic idea of using a piston airframe as a basis for the design of a jet was suspect from the start but the beancounters, I am sure, loved the idea. "Think how much money we will save" ..... right!! We need a jet engine that will fit, why not use the one we use in the Jindivik? We can save money that way. Actually worked out to be a good choice. Don't bother to redesign any systems ....... wrong.

After all this compromise the people that made the project work were principled test pilots such as Lt Cdr Overbury. These are the people that took that bag of nails and said that this is acceptable, this is not acceptable, why don't we try this idea? These are the people that, in pre-computer days, stuck their neck out (and sometimes paid) and gave us aircraft that, whilst not being perfect, we knew about their faults and we could trust that if we stayed within the limits defined by the test pilots we would have no problems. We also knew clearly what we could expect if we had to operationally slide over the limits.
Your points are well made and compromise and reuse of existing designs from earlier aircraft was pervasive in the classic British designs of the 1950's as exemplified by the fact that most of the British aircraft of that era suffered from hydraulic and fuel system leaks because it was simply too much effort or too expensive to redesign such systems from scratch, many of these designs having been cannibalised or adapted from existing systems, some even from piston engine aircraft.

The Jet Provost, it seems, was no exception...
‘In our memorandum to you on the 25th October 1955, we concluded from our examination that the fire and explosion was due to the spontaneous ignition of free fuel in the rear fuselage. This free fuel most probably originated from the air relief valve when the vent system filled with fuel during aerobatics. The main contributory factor to the fire and explosion was the collection of this free fuel in the rear fuselage. The inefficient venting system discharge point and inadequate sealing of the skinning permitted this free fuel to enter the rear fuselage and ventral fin.’

Accident to Jet Provost XD680 on 1-9-55, Accidents Investigation Branch, 15 November 1956 (PRO (AVIA 5/34)).

Dramatic as this sounded, the aircraft was soon back on the evaluation programme. The problem of free fuel igniting in the rear fuselage of aircraft was not a new phenomenon, as the AIB readily noted. Similar problems had been encountered in Vampire, Venom and Hunter aircraft, and this had been partially rectified by the addition of suction vents. This required a series of drain holes to be placed along the underside of the aircraft, which were then fitted with suction fairings. The idea was that the fairing induced a negative pressure below the drain and sucked out any residual fuel and vapours.
Jet Provost, The Little Plane with the Big History – Bob Clarke

I also remember seeing fluid leaking in situ into drip trays out of the English Electric Lightning at Thunder City back in the day and the military history of the type shows that fires and losses to due to hydraulic and fuel leaks also occurred throughout that type's history as well.

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Re: Test Pilots - The Good, the Bad and the Ugly!

#9 Post by Boac » Sat Jun 23, 2018 10:30 am

Caco wrote:I also remember seeing fluid leaking in situ into drip trays out of the English Electric Lightning
- I think I posted elsewhere that if there was NOT a pool of fuel under your beast when you checked it out, one summoned the line NCO and asked why it had not been refuelled.....

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Re: Test Pilots - The Good, the Bad and the Ugly!

#10 Post by ian16th » Sat Jun 23, 2018 12:14 pm

Cacophonix wrote:
Sat Jun 23, 2018 8:12 am

Accident to Jet Provost XD680 on 1-9-55, Accidents Investigation Branch, 15 November 1956 (PRO (AVIA 5/34)).

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Re: Test Pilots - The Good, the Bad and the Ugly!

#11 Post by boing » Sat Jun 23, 2018 2:50 pm

The Viper engine of the Jet Provost really deserves special mention. It would probably win an award as the jet engine that spent the highest percentage of its operating life at 100% RPM.

The radio call prior to a formation training "tail chase" was something like "Set 95% RPM, follow me, follow me, go". Probably less than 30 seconds into the sequence all three aircraft would have the power lever firmly on the forward stop and it stayed there until the tail chase was over.

During both aerobatics and circuit training the engine spent a lot of its time at 100% and it was subject to slam accelerations and decelerations that would have destroyed other motors. It was one very tough engine.


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Re: Test Pilots - The Good, the Bad and the Ugly!

#12 Post by boing » Sat Jun 23, 2018 3:02 pm

During my service time I had the real pleasure of working with three test-pilots, a small sample I admit. They were all without doubt very fine pilots, fine company and surprisingly matter-of-fact about their achievements but I have so say that all three were somewhat "spacey" in their routine lives. An example I remember is one of them who arrived in the Mess bar at about 19.00, spent the whole evening having a few beers and generally socializing with the guys, then, as the bar was closing remembered he had come to the Mess originally to see if he could find some Aspirin as his wife had a headache !!

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