Napier Sabre engine reliability

[Calladhor]

Although the Sabre engine successfully passed its type test in June 1940, problems started to manifest themselves as soon as volume production started. At the time, it was not only the world's most powerful aircraft engine, but also the most complicated, and in many areas not only advanced the state of the art for high-performance engine design but in manufacture as well. This established the scene for an unfortunate set of circumstances that were never satisfactorily resolved.
The engines used for the type test had been hand built, hand fitted, and carefully assembled by Napier's top craftsmen at their factory in Acton, a suburb of London.
Production engines, on the other hand, were assembled in Napier's shadow factory in Walton, near Liverpool. The mass-produced engines did not have the luxury of being hand-built; resulting in many mechanical problems, particularly as the engines entered squadron service.
The majority of the problems centred on the sleeves and sleeve drives. Most of the issues were resolved when the Bristol Aircraft Company, who, at first had refused to cooperate with Napier to manufacture Sabre sleeves... (as at that time, Bristol were developing their own sleeve valve designs, and their Taurus engine had the same bore)... objecting on the grounds that their manufacturing methods were confidential; were "encouraged" by the Air Ministry to get involved in the production of sleeve valves.
As a result of this intense pressure, they relented, and the problems soon disappeared with Sabre sleeves being manufactured from nitrided austenitic forgings using Bristol tooling, thus making a major contribution to the saving of the entire Sabre programme.

[DH82EH]

Interesting post.
Thanks for that.
Welcome to WIX.

Andy

[Dave Hadfield]

Yes, good points. Not new however.

A good book about the intro to service of the Sabre is Cocky Dundas' Flying Start.

https://www.amazon.co.uk/Flying-Start-H ... 1848844425

And a very good understanding of the complexity of the engine can be inferred from this animation of a radial sleeve-valve:

https://www.youtube.com/watch?v=_vrvep_YOio

And here is footage of the actual movement of sleeves in a Sabre.

https://www.youtube.com/watch?v=GjciUTgvqew

Dave

[Aeronut]

I used to work with a chap who had been an apprentice at Napiers and he remembered Sabres being returned to the factory for inspection. on stripping the engine the pistons and crankcase (both Al alloy) were in tolerance but the steel sleeves were badly worn which they initially found puzzling. Use of Microscopes revealed grit embedded in the softer alloy turning the piston and crankcase into grinding surfaces, wearing away the sleeves. These engines had come from aircraft operating from the dirt strips in Normandy before the changes were made to filtration of the intact air.

[exhaustgases]

I guess by the term "hand built" you mean spending time to get tolerances as close as possible. In this day and age saying something is not hand built, means that a machine has built it. In those days EVERY aircraft engine in all the different countries WERE hand built. All you have to do is look at all the old movies on the subject and you see a lot of men and women that are HAND assembling the aircraft engines. So to sum it up every aircraft engine in the WWII days was HAND BUILT.
And after they were first test run, they were then taken apart and inspected, so they got hand built twice before leaving the factory.

[phil65]

"And after they were first test run, they were then taken apart and inspected, so they got hand built twice before leaving the factory."

I kind of doubt they took the engines apart again. Do you have proof of this ?

Thanks,
Phil

[Hawker_Typhoon]

"And after they were first test run, they were then taken apart and inspected, so they got hand built twice before leaving the factory."

I kind of doubt they took the engines apart again. Do you have proof of this ?

Thanks,
Phil

Phil, I can confirm that the engines were stripped and measured after the initial break-in period, then re-assembled and tested again (although not as extensively as after the first runs). Initially we thought this was limited to early engines, but our understanding is that it was a process used throughout production.

Ian Slater
http://typhoonlegacy.com/
https://www.facebook.com/hawkertyphoonjp843/

[ZRX61]

Napier had their apprentices section old engines, which explains why most of the surviving Sabers (& Lions) have gaping holes in them.