Comet original engines

[Tevios]

I am after some more info for my book. I would like to know what the original engines were on the Comet? They were a bit underpowered which led to the skin of the aircraft being reduced to save weight. What were the American engines called that should have been used?
Would much appreciate reply.
Chris

[DozyWannabe]

Er, no plan to fit it with US engines existed.

The engines fitted to the Mark 1 Comet were De Havilland Ghosts. The preferred engine, fitted to Mark 2 and later, was the Rolls-Royce Avon.

[TheChitterneFlyer]

Tevios,

I'm not sure where your source of information is coming from, but the Comet skin certainly wasn't reduced to save any weight. An increase in overall weight occured because of the neccessity to 'armour plate' the engine bay walls. This was done to protect the wing/fuselage structure from the possibilty of any turbine shedding from the the engine(s); which would cause catastrophic failure of the surrounding structure.

As DozyWannabe quite rightly states... there was never any plan to introduce an american engine. The Ghost 50 Mk1 engine was severely underpowered. Originally, De Haviland had planned to fit two Sprite 'booster rockets' to improve take-off performance at hot and high airfields such as Nairobi; however, after some thirty test firings, it was concluded that they weren't neccessary. The later AJ65 Avon engines produced much higher levels of thrust from a less heavier engine.

TCF

[Tevios]

Thanks for info so far. It's easy to get thing wrong. Did the Comet start off with square shaped windows and did this lead to metal fatigue?

[Aeronut]

Hmmmmm, can't wait to read this book.

[chiglet]

Tevios..........
Type into "Google"
De Haviland Comet.....
You should have enough info for a Series of Books :ok:

[chevvron]

Aah De Havilland (2 L's)!

[JW411]

I thought the original DH Comet was powered by two uprated versions of the Gypsy 6.

[PFR]

Tevios - you're not getting confused with another fine "British Aeroplane" are you - the 1-11? Now there were plans to fit US engines to that - the mighty JT8D - shame it didn't come off as that would have given the "yanks" a run for their money:ok:

[Tevios]

I have looked up the info on google as suggested. Why I didn't do this in the first place... Anyway, square navigation windows were to blame for catastrophic metal fatigue leading to the loss of aircraft. The American CAA, interestingly already had misgivings about the square windows and would not issue an airworthyness certificate. The book I'm writing is only an Autobiography, but if you refer to anything you have to make sure of your material.
Nontheless, thanks for your help.

[parabellum]

given the "yanks" a run for their money


Weren't the "yanks" the biggest single operator of the BAC1-11? I think it was called Allagheney Airlines in those days, or was the BEA/BA fleet bigger?.

[ICT_SLB]

Tevios,
I think you'll find it wasn't "navigation windows" but the square cut-outs for the ADF loop antennas that was identified as the initial point of the failure of the fuselage.

Parabellum,
I beleive the largest initial fleet was American with 30, Mohawk had 18. The best site on the 1-11 is here (http://www.bac1-11jet.co.uk/) Ironically the last attempt to improve the 1-11 was by an American company, Dee Howard, that successfully installed Rolls Royce Tays but couldn't complete the certification as BAe wouldn't (or couldn't) release the original data.

[PFR]

You're right ICT_SLB re the 1-11 and the Tay, sad as that may be:ugh: (BAe were concerned for potential sales impact on the BAe146, especially if the Romanians could produce the airframe cheap, and it's fair to say Airbus wouldn't have encouraged BAe either with the A320 coming on stream). But for sure if the a/c had been offered at its inception with the US engine, sales would have no doubt been even greater in the States. It says a lot for the a/c that it sold in the numbers it did with just the Spey.

Tevios - if you want a good history of the Comet ("other good Comet books are available") go see a copy of Timothy Walkers book "The First Jet Airliner: The Story of the De Havilland Comet" (ISBN 1-902236-05-X), Scoval Publishing Ltd. Hope that helps...

PFR

[forget]

ICT_SLB.
Tevios, I think you'll find it wasn't "navigation windows" but the square cut-outs for the ADF loop antennas that was identified as the initial point of the failure of the fuselage.

Correct.

http://i21.photobucket.com/albums/b270/cumpas/comet-1.jpg

[merv32249213]

In 1956 fresh out of the airforce, I started with Marshalls and was placed on the three Ex BOAC Comet2 conversions for the RAF
I was involved in fitting of the Titanium firewalls between the enginebays and also the hardware prior to the Avons being fitted.What a job as anyone will testify when drilling Titanium ,I still have the scars.
Another large Mod I was involved in was the fitting of the "Droop snout" profile leading edges (hundreds of anchor nuts to fit ) and new engine air intakes. If my memory serves me right these were to help with low speed problems, and a cure for the Comets having too smooth airflow around the intakes resulting at certain angles of attack, a blanket effect to the inboard engine airflow.

A look at the earlier Comets compared to later ones and you will see what I mean,a protuding top leading edge to the intakes.

Later, working on the Comet 4 assembly line at Hatfield, I seem to remember going over to the other side of the airfield to see an old mate of mine ,"Olly Wood" and he showed me round a Ghost powered Comet of the MOD. Having worked on Ghost engines in the RAF it was very interesting to compare
Merv

[FlightlessParrot]

The claim that the Comet's skin was made thinner to compensate for the low thrust of the Ghost is made in the Wikipedia article on the DH Ghost.

This is certainly the first time I've heard such a claim, but that doesn't prove much. Any truth? Or is it a misunderstanding of the design constraints on early jets.

I remember going to Hatfield on a jolly from school, and seeing Comets being glued together.

[WHBM]

Tevios - you're not getting confused with another fine "British Aeroplane" are you - the 1-11? Now there were plans to fit US engines to that - the mighty JT8D - shame it didn't come off as that would have given the "yanks" a run for their money
This is not necessarily so. The Caravelle was launched with Avon engines (turbojets no less), and was a major sales success. They then offered the JT8D, a fan jet, as a major development. Sales were poor for this variant, none to the Americans at all (the one US fleet of Caravelles, with United, chose Avons), and Sud probably didn't even get their money back from the JT8D project.

[barit1]

A late mark Caravelle was test flown with GE CJ805-23 aftfans (same as the CV990) - but no sales resulted. After the program was cancelled, the ship was restored to standard configuration and sold.

[Brian Abraham]

The claim that the Comet's skin was made thinner to compensate for the low thrust of the Ghost is made in the Wikipedia article on the DH Ghost
Designers are forever attempting to keep the empty weight as low as possible, for every pound saved is an extra pound of payload or fuel. Has ever been so. It is said in some quarters that the reason the aircraft had very little paint (natural metal finish) was another endevour to reduce weight. The low thrust available and the high fuel consumption of course were an anvil on performance/capability. The fuselage skin was .028 inch thick.

[merv32249213]

Another weight saving on the Comets was the Redux process , to attach stringers to the skin. This was a common process used by D Hs on most of their aircraft at that time,Doves and Herons etc. Think of the glue looking like rasberry jam between two pieces of metal, then heated, and then think of all the weight of rivits not required,some weight saving! .

Merv

[PFR]

Interesting WHBM but from accounts I hear of the Caravelle any poor sales success was much to do with the French, well being French:}. Product Support was poor and by the time the JT-8D variant was on offer there were home grown US engined competitors. Stories had it that it was not uncommon for the Vickers/BAC Rep in United to be asked to help with support issues on the Caravelle, in particular with British equipment fitted, simply because of the language barrier. Something Airbus took real serious when they put their minds on getting that product established in the States. By all accounts the Caravelle was well engineered and good operationally - no surprise some would say considering the point end was a Comet!:ok:

[Flight_Idle]

Plenty of information here about skin thicknesses, http://redirectingat.com/?id=42X487496&url=http%3A%2F%2Fnaca.central.cranfield.ac.uk%2Freports%2Far c%2Frm%2F3248.pdfwindow radii ect here...

[Jig Peter]

The mention of the Redux bonding process reminds me that (IIRC ...) the Caravelle's nose was built up at Hatfield on the Comet jigs, being easier and cheaper than "conventional" riveted stringers for such a complicated shape. An early example of deH and Aerospatiale cooperation which blossomed with the A300 programme ...

[chevvron]

Years ago, (mid-late 80s) I flew to Hatfield with Talkdownman to see '146s being glued together.

[Warmtoast]

.....memories

http://i145.photobucket.com/albums/r231/thawes/CometG-ALYP-Departure.jpg

Comet G-ALYP in happier days

[VX275]

Does the Comet's nose/cockpit hold the record for the most aircraft types its been flown on (Comet/Nimrod, Caravelle, Horsa) ?