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GOT: The AVRO Tudor 688 - 689

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#1 Romantic Technofreak

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Posted 21 December 2005 - 02:39 AM

This time. friends, it was hard to retrieve information, especially about the AVRO 688 Tudor I, unless another German (*Jemiba*) from airwarfareforum provided me an article from "Aeroplane Monthly", written by John Stroud and issued December 1993. I could have made it easy to myself and just upload it, but I thought, for readability and combination with the other few information I have, to shorten and to rewrite it a bit. Also, I could change the size to a comfortable one, including the one of the pictures.

So, after having a start looking at the nose of Tudor IV "Elizabeth of England" G-AGRF,

TB01.jpg

let's have the begin for the


AVRO 688

Tudor I

The AVRO Tudor wasn't a great success, rather the contrary. Combining the wing of the great Lancaster with a completely different fuselage didn't show to be the best idea.
The construction of the AVRO 688 based on recommendations of a committe under the chairmanship of Lord Brabazon of Tara, which between late spring 1943 and autumn 1945 made gave specifications for not less than nine types of commercial transport aircraft for post-war use.
To meet one of these recommendations, A.V.Roe & Co. Ltd. first decided to build the AVRO 687 or AVRO XX, merely a Lancaster IV/Lincoln bomber with a new circular-section pressurized fuselage, and a large single fin and rudder in place of the predecessors slim double ones. During the design stage, the mere conversion idea was abandoned and the constructively more distant AVRO 688 was schemed (although I cant say which were the basic differences between AVRO 687 and 688, RT). The drive system ove four Rolls-Royce Merlin liquid-cooled engines was retained. Two prototypes were ordered, in Septdember 1944, and the first one flew on June 14th, 1945, and was the first British pressurized transport aircraft, although it originally flew unpressurized.

The AVRO Tudor I prototype G-AGPF:
TB02.jpg

When I (RT) was asking for help on airwarfareforum.com, honoured contributor Ton Meynders provided me, besides pictures, an article from Aeroplane Spotter 1945/46 about the first flight of the AVRO Tudor: (link dead) http://www.airwarfar...pic.php?t=5008

The Tudor I was intended for North Atlantic operation. At the time it was designed the USA had the Douglas DC-4 and Lockheed Constellation, so the less said the better about designing a four-engined pressurized aeroplane of some 70,000 lb all-up weight and nearly 7,000 hp for 12 passengers. Nevertheless, in November 1944 the Ministery of Supply ordered 14 Tudor Is for BOAC, and in April 1945 increased the production order to 20!
The Tudor was a low-wing cantilever monoplane with four engines, a single fin and rudder and a retractable tailwheel undercarriage. The DC-4 and Constellation had nose-wheels instead.
The wing, of NACA 23018 section at the root, was a five-piece all-metal two-spar structure. The untapered centre section carried the inboard engines and main undercarriage sections. The inner and outer sections were tapered on their leading and trailing edges, and had a 2 degrees four minutes dihedral on the top of the front spar, with the inner sections carrying the outbound engines. The spar booms passed through the fuselage in rubber-scaled shrouds. The ailerons had trim and balance tabs, and there were hydraulically operated split flaps in three sections on each side of the trailing edges of the centre section and inner wings. The 3,300 Imp gal fuel capacity was provided by eight crashproof bag tanks, on on either side of the fuselage in the centre section and three in every inner wing.
The circular cross-section wing was an all-metal semi-monococque structure with 10 ft. maximum diameter. Above floor level there were inner and outer skins with kapok filling. The metal tail unit had a dorsal fin built integrally wit the fuselage, a 43 ft. two-spar tailplane with inset divided elevators. The control surfaces were mass-balanced, and each had controllable trim and servo tabs.
The hydraulically operated main-wheel units were similar to those of the Lancaster, had single Dunlop wheels and retracted rearward into the inboard engine nacelles. The twin tailwheels retracted rearward into the fuselage and were enclosed by twin longitudinal doors.
The prototype Tudor I had 1,750 hp Rolls-Royce Merlin 102 12-cylinder vee liquid cooled engines. The first production airplane originally had these engines, but standard engines were 1,770 hp Merlin 621s. They were enclosed in circular section nacelles and drove 13 ft diameter Rotol four-bladed constant-speed fully feathering propellers. There were underslung radiators and large spinners.
The crew section was arranged for two pilots, a radio operator, a flight engineer and a navigator - an operating crew of five for 12 passengers (where are the stewards?, RT). There were different equipments for a lot of different passenger numbers, from 12 up to nearly 80, as we will see later. When the author of the Aeroplane Monthly article flew in the machine (G-AGRC) on May 1st, 1946, it could contain only 12 passengers. The author notes he was the first person getting served a whiskey at 25,000 ft in a British transport airplane.

Two views of G-AGRC:
TB03.jpg

TB05.jpg

At that time, AVRO performance figures for the Tudor I were "Maximum all-out level speed 346 mph at 20,500 ft, maximum cruising speed 300 mph at 22,500 ft, sea-level rate-of-climb (78,000 lbs) 800 ft/min, service ceiling (4 engines) 28.000 ft, service ceiling (3 engines) 22.700 ft, range-payload 24-seat version 3,730 miles with 24 passengers, 50 lb of baggage each, and 3,300 lb of mail, range-payload 12-seat version 4.400 miles with 12 passengers, 100 lb of baggage each and 3.300 lb of freight".

G-AGRF, the fourth production airplane, was named Elizabeth of England by HRH Princess Elizabeth in a ceremony at London Heathrow Airport on January 21th, 1947, but the airplane never went into service with BOAC.

TB04.jpg

The Tudor I suffered a number of problems, including longitudinal and directional instability. This led to the fitting of a larger tailplane, and replacement of the finely curved fin and ruddr by extremely ugly bigger vertical surfaces. Pre-stall buffet was cured by modifying the wing-root filletsand extending the inboard engine nacelles. Various other shortcomings were revealed. BOAC added to the delays with more than 340 modifications, and finally the airline rejected the Tudor I on April 11th, 1947, judging it incapable of North Atlantic operations.
It had been intended that 12 Tudors would be built in Australia for military transport, but this plan was abandoned.
Twelve Tudor Is were built. Of these three were scrapped. G-AGRE became the prototype Tudor 4B, G-AGRF was converted to Tudor 4B, 'RG and 'RH became Tudor Freighter Is (later Super Trader 4 and 4B), 'RI and 'RJ went to Aviation Traders and were used by Air Charter, 'RK and 'RL went to the Ministery of Supply as TS874 and TS875 and were dismanteled in December 1950, and G-AGST was rebuilt as Tudor 4 and eventually became the Tudor 8. There is a table given below including all Tudors.

At this point, I have to do a break with the original sequence of the article. It continues in the sequence of Tudors in Roman numbers, but I would like to go on in a way to show which version was an AVRO 688, and which one a 689. The table mentioned above and given below shows, that Roman digits I, III, IV (mostly written in Arab as 4 and 4B) are 688s, II, V, VI and VII are 689s, VIII is basically a 688, but in my eyes a very different aircraft, so I put it to the end of my article again. Here, I now mention the digits III and IV first, before leaving for the 689.

Tudor III

Two Tudor I-sized aircraft, G-AIYA and G-AJKC, were sent to Armstrong Whitworth to be completed as luxury transports for Cabinet Ministers. They accomodated nine or ten passengers by day and had nine berths. They became VP301 an VP312, and both were acquired by Aviation Traders in September 1953, VP301 being re-converted into a Tudor I.
In 1955, G-AIYA and the Tudor I G-AGRG were lenghtened to Tudor IV standard. Together with the unlengthened Tudor I G-AGRI, which had become a 42-seat passenger aircraft, they were used on Colonial Coach Services between the UK, Tripoli and Lagos.

Tudor IV

To meet a BSAA (British South Atlantic Airways, RT) requirement, some of the Tudor Is were lenghtened by 5 ft 9 in and powered by 1,770 hp Merlin 621s and 1.760 hp Merlin 623s. With 32 seats and no flight engineer's position, these were known as Tudor 4s (IVs to Avro), and with flight engineer's position and 28 seats Tudor 4Bs. These conversions were covered by specification 28/46B and the first example, G-AHNJ Star Panther, first flew on April 9th, 1947. The Tudor 4 received its C of A (commitment of authorization? Help! RT) on July 18th, 1947, and on September 29th BSAA took delivery of its first airplane, G-AHNK Star Lion. The next day, under the command of D.C.T. Bennett, it left Heathrow on a proving flight to South America. On October 31st, Star Lion inaugurated Tudor services from London to Havana via Lisbon, the Azores, Bermuda and Nassau.

Tudor IV serial machine G-AHNN:
TB10.jpg

But in the night of January 29th to 30gth, 1948, Star Tiger G-AHNP with 31 people on board disappeared between the Azores and Bermuda (triangle! RT), and the type was temporarily grounded. Although the cause of the loss was not established, Tudors went back into service and on December 3rd, 1948, began operatinga weekly service London - Keflavik - Gander - Bermuda - Kingston - Barranquilla - Lima - Santiago - Buenos Aires, returning via the Azores instead of by the northern route.
One more disaster struck. G-AGRE, Star Ariel, disappered on January 17th, 1949, between Bermuda (triangle! RT) and Kingston, with the loss of 20 of its occupants, and Tudor was agian grounded. The subsequent fleet shortage led to the merger of BSAA with BOAC.

Being a favourite of supersensual events, I prefer the Bermuda Triangle as reason. However, Norman Ridell, RAF veteran and BSAA Flight Captain, doesn't. He points on structural flaws within the (changed) tail section. See this link: http://www.far-easte..._adventure.htm

I (Mr. Stroud, RT) believe that the cause of the Tudor losses was never established, but pressurization problems were suspected, and the remaining aircraft were flown as unpressurized freighters under the designations Tudor Freighter 4 and 4B.
Sharing of the Tudor 4 within the Berlin Airlift see Tudor V. Of the 13 Tudor 4s built, 8 were acquired by Aviation Traders at the beginning of September 1953. G-AGRH, -AHNI, 'NM and 'NO were given 6 ft 10 in x 5 ft 5 in cargo doors aft on the port side. These were designated Super Trades 4 or 4B, and received their C of A in March 1955. Some remained in service until 1959. This year, on April 23th, G-AGRH Zephyr suffered the last spectacular Tudor crash on its way to Australia, in a mountaineous and nearly inaccessible region in Turkey. Because it probably carried classified material, the wreck was subsequently object of a complicated salvaging action.

See this lenghty link for details: http://www.rafmounta...d Chapter 5.htm



AVRO 689


Tudor II

I cannot quote it exactly, but to me it seems that the passenger capacity of the AVRO 688 from the beginning was considerd unsatisfactory, so a bigger version was in planning from the very start. Bearing the AVRO type number 689 and also known as AVRO XXI, the Tudor II was designed as 60-passenger plane for the BOAC. It was essentially the same as the Tudor I, but the fuselage diameter was increased from 10 to 11 ft and the overall lenght was 105 ft 7 in compared with the Tudor Is 79 ft 6 in.
Towards the end of 1944, while the aircraft was still in the design stage, BOAC, Quantas, and South African Airways decided to standardize on the type for Commonwealth routes, and the original BOAC order for 30 was increased to 79. However, none of the airlines operated Tudors, and nor did the BEA operate the type 699 version (short-range, RT) planned for it. The prototype, G-AGSU, first flew on March 10th, 1946, with Rolls-Royce Merlin 102s and the curved vertical tail surfaces originally used on the Tudor Is.

Tudor II prototype G-AGSU with original tailfin:
TB07.jpg

The airplane went to Boscombe Down for its certification trials, and the engines were changed to 1,740 hp Merlin 600As. The trials showed up problems similar to those encounterd with the Tudor I, and G-AGSU was returned to AVRO for extension of the inboard engine nacelles and fitting of the larger fin and rudder. Increased weight owing to the bigger fuselage and the other necessary modifications reduced performance so much that the type could only operate Eastern routes as far as Calcutta and the African routes not beyond Nairobi. Quantas and South African Airways could not use the Tudor II, and the order was cut back to 50 aircraft.

Tudor II prototype G-AGSU with changed tailfin:
TB09.jpg

G-AGSU crashed just after take-off on August 23th, 1947. Among the casualtiess there was nobody less than Roy Chadwick, AVRO chief designer and praised constructor of the Lancaster, and AVRO chief test pilot Bill Thorn. No design flaws were reasons of the accident, but an incorrectly mounted aileron control, setting it into the reverse direction than intended.

Read about Roy Chadwick in this link: http://www.suchiu.co...er_history.htm

An undated AVRO leaflet on the Tudor II - but showing it with the original tail unit - quoted the following performance figures: "Maximum all-out level speed 330 mph at 20,500 ft, maximum cruising speed 285 mph at 22,500 ft, sea-level rate-of-climb (80,000 lbs) 870 ft/min, service ceiling (4 engines) 28,600 ft, service ceiling (3 engines) 22,400 ft, range-payload 2,000 miles with 60 passengers and baggage, 2,600 miles with 40 passengers and baggage, and 1,000 miles with 9 tons of freight". The same leaflet contained a cutaway drawing, showing the layout for 40 passengers or 22 in sleeping berths. This was desribed as the BOAC layout.

What you see here is the main cabin of a Tudor II:
TB06.jpg

The second Tudor II completed, G-AGRY, went to Nairobi for tropical trials as VX202, but these were considered unsatisfactory and Tudor II orders were then reduced to 18. These should have been produced as two Tudor IIs for experimantal work, ten with nosewheel undercarriage as Type 711A traders to specification 23/48, and six as Tudor Vs to meet BSAA requirements and covered by specification 39/46.

G-AGSV, which was intended to be the 711A prototype, was not completed. G-AGRY received a C of A in September 1948, went to Airflight and was later used by Fairflight and Air Charter before being scrapped in July 1959. G-AGRZ went to Flirht Refuelling and later to Aviation Traders, and G-AGSA was lent to Rolls-Royce. Including the prototype, only four Tudor IIs were completed.
However, the six Tudor Vs were built and we continue with their story.


Tudor V

The Tudor V was a moification of the Tudor II, specification see above, with 44 seats. BSAA acquired five powered by 1,770 hp Merlin 621s. However, these aircraft never went into passenger service with this airline. Instead, they were stripped of furnishing and were used as fuel tankers on the Berlin Airlift. The first example, G-AKBY, of airline Airflight, as well as BSAA's G-AKBZ, 'CA, 'CB, 'CD and 'CD, together with BSAA's Tudor 4s G-AGRH and G-AGRJ, were on the way through Soviet-controlled airspace and back. BSAA statistics mention 2,562 sorties in 6,973 hours, carrying 22,125 tons of fuel into the besieged city.
Ill fate returned when G-AKBY, still operate by Airflight and now in passenger sevice, crashed at Llandow in Wales on March 12th, 1950, killing 80 of its occupants, Welsh rugby supporters. The aircraft was returning from Dublin, where the Welsh team just had won the Triple Crown. The accident was considered worst aviation desaster at this point of time. There are two very interesting links about the theme, one from the South Welsh Police Museum:

http://www.south-wal...8&n2=253&n3=689

and one from the Aviation Safety Net, giving a reason for the crash:

http://aviation-safe...p?id=19500312-0

G-AKCA was sold to Surrey Flying Services, and then loaned to Lome Airways in Canada as CF-FCY. G-AKCC and 'CD went to William Dempster and were converted to 52-seaters for London-Johannesburg tourist flights. G-AKCC was named President Kruger, but was damaged beyond repair at Bovingdon on October 26th, 1951, after which 'CD was used for spares.


Tudor VI

This version was mentioned to be built for the Argentinian airline FAMA (Flota Aerea Mercante Argentina) for services across the South Atlantic, with 32- 38 seats for daytime or 22 sleeping berths. None was built.


Tudor VII

One example, G-AGRX, was built. This was the first production Tudor II, powered by 1.750 hp Bristol Hercules 120 air-cooled radials in an attempt to give the Tudor II more satisfactory performance. It first flew on April 17th, 1946, and appeared at this year's SBAC (??, RT) display at Radlett. In June 1948, this aircraft was fitted with a shorter undercarriage, and the engines were inclined to provide greater ground clearance for the propellers.

TB08.jpg

The Tudor VII was used for cabin temperature trials, passed on to the Telecommunictions Research Establishment as VX199 and then went to Flight Refuelling in November 1953 under its civil registration. In March 1954, it was acquired by Aviation Traders for spares.

See the end section far down below because of picture limitation (08/04/2013)



#2 PMN1

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Posted 21 December 2005 - 02:59 AM

Bloody good bit of information there - dont think I've seen so much in one place, what do you have on the Handley Page HP.68 Hermes??

Also what would have replacing the Merlins with Pennines (had they been continued with) have done for performance?

Or replacing the Merlins with Hercules as the HP Hermes had?



#3 GregP

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Posted 21 December 2005 - 07:49 AM

Hi RT!

A great writeup! I didn't know that much information on the Tudor existed!

Thank you, yet again.

The Tudor 8: Span: 36.58m, Length: 32.18m, Height: 7.39m, WIng Area: 132.0sq.m, Engines: 4 x Rolls Royce Nene of 22.2kN each, Empty: 21000kg, Loaded: 36287kg, Max Speed: 768kph, Cruise Speed: 645kph, Range: 4100km, Ceiling: 8900m, Don't know how many built.

#4 PMN1

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Posted 21 December 2005 - 06:30 PM

Any idea of what kind of structural changes were needed to make it a nose gear aircraft for the Nene version?

#5 Romantic Technofreak

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Posted 22 December 2005 - 02:36 AM

Thank you for your answers, friends!
 

quote:Greg wrote:
I didn't know that much information on the Tudor existed!

I also didn't, until I cried for help and Jemiba came up wit that article!
 

quote:PMN1 wrote:
what do you have on the Handley Page HP.68 Hermes??

I have a bit, but I don't know if it were sufficient for a GOT topic (they already have some quality status, you know;)). The Hermes is not yet on Greg's list (could be placed on it; with Greg's permission! ;))
 

quote:PMN1 wrote:
Also what would have replacing the Merlins with Pennines (had they been continued with) have done for performance?

I don't know this kind of engine. Could you give me the performance?
 

quote:PMN1 wrote:
Or replacing the Merlins with Hercules as the HP Hermes had?

I suppose the performance you mean with 2,130 hp. I take 4 x 1,770 hp and 295 mph as base. Applying the cubic root formula, I estimate a Tudor with 4 x 2,130 hp would run 314 mph.
 

quote:PMN1 wrote: Any idea of what kind of structural changes were needed to make it a nose gear aircraft for the Nene version?

Sorry, this is a true engineering question and far beyond my scope as a hobby historian.

Regards, RT



#6 PMN1

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Posted 22 December 2005 - 04:19 AM

quote:Originally posted by Romantic Technofreak

Thank you for your answers, friends!

 

quote:PMN1 wrote:
Also what would have replacing the Merlins with Pennines (had they been continued with) have done for performance?

I don´t know this kind of engine. Could you give me the performance?



 

Rolls Royce Pennine - 24 cylinder (6 rows of 4 cylinders), sleeve valve air cooled, 44 litre engine developed from the Exe, planned to develop 2,500hp.

Not sure about the frontal area but i'm pretty sure it would be less than an equivalent radial.



#7 Romantic Technofreak

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Posted 24 December 2005 - 03:23 AM

With 10,000 hp, I calculate a speed of 330 mph for the Tudor.

Regards, RT

#8 ChrisMcD

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Posted 06 January 2006 - 04:44 AM

Hi RT

Looks like the tudor had real aerodynamic problems

"The Tudor I was the first British pressurised transport, and right from the start it was in trouble. It suffered from directional and longitudinal instability, pre-stall buffeting at a relatively high speed, violent rudder oscillation at moderate angles, severe take-off swing, loss in performance from that estimated, and a tendency to bounce on landing.

The instability troubles were solved by fitting a larger fin and rudder and larger tail plane and elevators, but the real crunch was the performance loss which reduced the still air range from an estimated 4,000 miles to an actual 3,600 miles and so made the Tudor a non-starter for the Atlantic route.

It was at this point that the R.A.E. Farnborough was called in to help, and Tudor I G-AGRD arrived there in the summer of 1946. This aircraft had already been fitted with the large tail empennage when I first flew it on 20th July, and in addition had been deep tufted at the R.A.E. for airflow investigation, i.e. wool tufts were placed on masts 3", 6", 9" and 12" from the aircraft skin on the whole upper surface of both wings, on one side of the body from the position of the wing maximum thickness down to the tailplane, including the fin-tailplane junction, on the top and bottom surface of the tailplane and elevator, and on one side of the fin and rudder. In addition, a trailing static was fitted - this is like a small bomb on the end of 100 ft. of tubing which transmits an airspeed reading free from all turbulence created by the aircraft. In the next few days I carried out intensive stalling tests and encountered such violent pre-stall buffeting that the trailing static was beaten to pulp, but not before we discovered that the stall previously reported by the A & AEE Boscombe Down was not the true stall. I found that by being extremely careful to prevent the pre-stall porpoising from building up, the speed could be lowered much below the previously reported minimum speeds, thro~gh intense and almost dangerous buffeting until a wing drop occurred.

Our observations showed that the apparent stall was caused by a deep and violent wing root breakaway of airflow, the resultant violent wake passing over the tail end of the aircraft. It was considered by R.A.E. that the obvious cure was to improve the wing root filleting. A new and large fillet designed by Avro was therefore fitted to another Tudor, G-AGST, which I first flew at Farnborough on 8th August 1946 on stall tests.
The qualitative tests seemed to indicate that the large fillet had been successful in curing the premature buffeting trouble in that there was now only 2-5 mph between the onset of buffeting and the stall as indicated by the wing drop. Quantitative measurements, however, showed a very different state of affairs, because the stalling speeds had increased up to 10 mph above those recorded before. It thus became clear we were dealing with two separate effects, viz. changes in inner wing condition leading to changes in the speeds at which buffeting occurred, and changes i~ outer wing condition leading to changes in the speed at which the wing drop stall occurred.
The inner wing problem involved considerable trial and error before it was pinpointed to a very small airleak around the leading edge of the wing root causing a break way of flow, the resultant wake of which hit the tailplane.
The early wing-tip stalling cause was easier to locate as due to small malfitment of the wing leading-edge de-icers spoiling the aerofoil contour.

The rudder oscillation phenomenon was first experienced during tests on G-AGRD to determine the adequacy of the directional control in the engine cut condition. As rudder angle was increased, especially when trimmer was wound on to trim out the rudder pedal loads, at a certain rudder angle violent kicking occurred on the rudder pedals, thus having the effect of raising the engine cut safety speed, as rudder angles above those at which kicking started could not be used.

This problem was soon traced to bad flow initiated by sharp edges at the rear of the three hinge cutouts projecting out into the airstream as rudder was applied. Modifications to G-AGST cured the trouble and reduced the engine cut safety speed from 130 knots to 100 knots at 80,000 lb. all-up weight.
The difficulty in controlling take-off swing, especially in a cross-wind, was mainly during the initial period of the take-off run which was long, due to poor acceleration, and aileron snatch and elevator buffet were experienced. Examination of the deep tufting on G-AGST during a take-off run showed clearly that the whole wing was completely stalled in the ground attitude; the ground incidence was 14 '120. Once the tail lifted, the airflow over the rear body began to clear. These flow conditions accounted for the poor initial ground acceleration, but the root cause of the trouble was the insufficient rudder power available for corrective action.

The cure for the take-off swing problem was a shortened undercarriage to decrease wing incidence on the ground, and increase in rudder power resulting from the modifications to the rudder hinge cutouts.
The deep tufting technique revealed another trouble spot on the Tudor, whose original inner-engine nacelles had been of the Lancaster type extending to the trailing-edge of the wing, but these had been shortened to finish at the flap hinge to eliminate vibration troubles. The new nacelles were observed at R.A.E. to have a complete breakaway of flow round their rather bluff ends. This turbulence of flow occurred over the whole speed range, and obviously the drag would adversely affect performance. R.A.E. therefore extended the inner nacelles some 18 ins. to 2 ft. behind the trailing-edge and these showed no sign of any flow breakaway over the speed range from slow cruising to top speed, and the vibration level was lowered appreciably from either ofthe other two nacelle designs.

On the 24th October 1946 I flew G-AGST back to the Avro airfield at Woodford, and although it had all the improvements recommended by R.A.E. fitted to it, I sensed instinctively that we had only patched up an inherently bad design, and that the Tudor was a loser. In the event British Overseas Airways Corporation shared this view and rejected the type by cancelling their order. Four of the cancelled aircraft were taken over by British South American Airways Corporation.

In April and May 1947 I was again engaged on tests on G-AGRD to see if the new wing de-icing installation had improved the stalling characteristics.
Since the Tudor I only carried 12 passengers, its commercial viability on that score alone was in question, so a stretched version was built to carry 60 passengers. This Tudor II was the largest aircraft so far produced in the U.K., but the increase in structural weight resulting from the stretching process reduced performance drastically, in spite of uprated Merlin 600 Special engines.
The Tudor II had an inauspicious start when the prototype G-AGSU crashed on take-off from Woodford on 23rd August 1947, killing Roy Chadwick. the Avro Chief Designer, and Bill Thorn, the Avro Chief Test Pilot. The crash was due to the incorrect assembly of the aileron circuit, whereby movements of the control wheel gave the reverse wing movement to that normally expected.
The next accident in the saga of Tudor disasters was the unexplained loss. of the BSAAC Tudor 4 Star Tiger N.E. of Bermuda on the night of 29th/30th January 1948.
Meanwhile, I renewed acquaintance with the Tudor I when G-AGRI came to Farnborough in July 1948 for a series of compressibility dives to assess the suitability of the airframe for fitting with jet engines. There were a few grim faces around the R.A.E. at the prospect of doing a job reserved for high-speed fighters to date, but I must admit the challenge rather intrigued me.
lt had been estimated that a Tudor fitted with four Nene engines for high altitude research purposes could have a maximum cruising speed of 435 mph true air speed at 40,000 ft. equivalent to a Mach number of 0.654, and that it might therefore experience some of the compressibility phenomena such as large changes of trim, tail buffeting, pitching, oscillations, etc. As the ceiling of the Merlin-engined Tudor I was limited to about 31,000 ft. the combination of lift coefficient and Mach number required could only be obtained by diving to reach the appropriate Mach number and applying 'g' in a pull out to attain the required lift coefficient. At an all-up weight of 61,000 lb. for the tests the estimated ultimate breaking 'g' was 4.35. .
For the tests I had a co-pilot, flight engineer, and a flight test observer. The drill I adopted was to find the trimmer settings which would trim the aircraft'at the maximum indicated air speeds of the dives when flying at 5,000 ft. The aircraft was then climbed to 31,000 ft. and cruised at maximum continuous power until airspeed had built up to'a steady value and the predetermined trim values set on the trimmers. The aircraft was then eased into a dive and the flight engineer set the engines to 2850 rpm with the supercharger in FS gear and the radiator shutters closed.
During the dive through several thousand feet, the co-pilot had his hands lightly on the control wheel to assist if I experienced any unmanageable control loads either due to compressibility effects or to execute the required pull-out 'g'. In the event the Tudor behaved perfectly up to a maximum true Mach number of 0.67 and a subsequent pull-out of 2.25 'g'. These values well exceeded what was required of the tests, so for once the Tudor had excelled itself.
Bad luck still dogged this unfortunate aircraft with the loss of Star Ariel
between Bermuda and Jamaica on 17th January 1949, again in unexplained circumstances. As a result BSAAC converted its Tudor 4s to freighters for the Berlin Air Lift and did 261 sorties on this operaton, while seven Tudor 5s flew 3,167 sorties in the tanker role.
These latter aircraft were refurbished for passenger work after the Berlin crisis and G-AKBY crashed at Llandow on 12th March 1950 when approaching to land after a charter trip from Dublin with a load of Welsh rugby supporters. The loss of 80 lives made this the biggest air disaster in the U.K. up to that time. The accident cause was determined to be incorrect loading.
This was virtually the end of a history of tragedy surrounding an aircraft that came from the same design team responsible for the magnificent Lancaster. The spark of genius failed to ignite in the Tudor, which exacted a grim penalty for that failure.




#9 Romantic Technofreak

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Posted 06 January 2006 - 03:59 PM

Thank you for your adding, Chris!

For myself, I draw the following conclusions:

1. Although the Tudor is considerably bigger than the Lancaster, it uses more or less the same engines. So it looks to be fairly underpowered. The calculations suggested by our friend PMN1 don't result in a big advantage. The time of the piston-engine-driven airliner is nearing the end at that time.

2. For the losses in the Caribic, I have to say that these planes, although equipped with pressurization (really installed? and did it work?) were unable to cross a hurricane by flying over it. Also, the weather forecast methods at that time and place were not so sophisticated as they are now. Many losses in the Bermuda triangle at that time, were owed to very bad and unpredictable weather circumstances, also to worse quality of used materials.

3. For the crash in Wales, I have to say that I don't see a Tudor version with eventually 80 seats installed. So the plane must have been overloaded. I also can imagine that the supporters, celebrating their victory, could have been alcoholized and on the on the landing approach did not keep seating discipline... :o :(

4. The last crash, in Turkey, reminds me to a frequently used "label" for crashes: "piloted into ground under full control". This means, the pilot must have lost orientation - due to bad weather circumstances again, night or whatever.

I have to say, that, except the first, these points don't speak against the Tudor. The aerodynamic troubles you quoted, Chris, were treated already some years before the losses I quoted above, so they should have been more or less solved at that time.

By the way, who wrote that article you posted?

Thanks again, and regards,
RT



#10 ChrisMcD

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Posted 08 January 2006 - 03:38 AM

Hi RT,

Eric Brown again!! He flew just about every German and British aircraft of the period and left good notes on most. Are you after any others??

I get the impression that Avro took too long to sort out the aerodynamics. Possibly distracted by the Vulcan?

As you say the crashes sound like they are not directly related to the aircraft.

Am working on Bv 138 info - have U boat photos and am looking for details of base on Novoya Zemyla - do you have any leads?






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