BAe-146/Avro -- Why Four Engines?

[MrSkyGuy]

Yes, I realize the obvious (and silly) answers, such as: "because three was not enough" or "five was too many", etc.

What I'm interested in is the design reasons why the BAe-146 was designed with four eggbeaters as opposed to two stronger, somewhat-larger engines. I understand that the aircraft has a higher redundancy reliability with 4 as opposed to two, but this seems to have been a bit overkill, even if engine noise is reduced. Twins are (in most cases) cheaper to maintain and it's always struck me as odd that BAe decided in favor of 4 small fans vs. two somewhat-larger ones. Certainly this is driving a faster retirement of even the newer Avro versions..?

I'd love to hear your feedback!

[powerstall]

a friend of mine who flies a BAe 146-200, told me the 146 was developed for STOL and noise abatement compliance. :confused:

Just my two cents, :E

[spekesoftly]

When 146 production finally started in the early 1980s (it went through a number of false starts due to company changes/1973 fuel crisis etc) suitable engine choice was limited. With an eye to the American market, where a number of airports* were already introducing much more stringent aircraft noise restrictions, four small engines was the only way of achieving the required power/sfc/noise compromise.

*I believe that in the early days, the 146 was the only public transport aircraft that could comply with the night-time noise restrictions at Orange County (John Wayne) Airport.

[Salusa]

I always assumed it had 5 APU's ;)

[powerstall]

5 APU's that produce thrust! :ok:

[MrSkyGuy]

Granted it's a quiet little bird, but historically economical use has been the driving force with successful jet sales. I'm surprised that at the very least the BAe didn't have a twin option at some point.

[mrmagooo]

There was once a model at BAe Woodford, albeit a small one (about 2 foot long) that had two engines.

Two larger engines would reduce ground clearance and hence not be as good when used on rough landing strips

[steve wilson]

The 146 was designed for rough/ short strip operations. In addition to the given John Wayne Airport I think its the only jet that can operate out of Jersey (JSY) and until recently London City (LCY).

The RJX, which was the replacement 146 was cancelled by BAE systems as it was upa against the Dornier 728 and the old C-Series. With just 30 orders from Fly BE thay caned it, whoch seems a shame as the 728 bit the dust and the C-Series went offline for many years before it was reborn. Maybe a twin-engine RJX would fo sold better.

I think that BAE missed a mark here. Going off at a tangent a little, but............

How many mew build, long range. 4 engine MPA can you buy for an Airforce today? None. With all the cash that is being spent developing the Nimrod MR4, they are going to gain 0 export sales. Why, lack of airframes.

The RJX would of been easy to double-bubble and add sensors to. At low level on patrol two of the four engines could be idled.

Shame.

Steve

[old,not bold]

The 4-engine configuration was advantageous for STOL operations and/or hot/high work, always a British obsession (VC10 et al).

Another reason might have been what I was shown in 1980 at Hatfield when evaluating the aircraft; a spare engine could be carried in relatively few boxes in the hold, being quite small; this was meant to be hugely attractive.

My boss at the time, an engineer who ran an airline, said when I reported back to him about this fantastic benefit, "you silly sod; why do you suppose they think it's necessary to have a spare always available?"

Except he wasn't so polite.

[WOTME?]

Bring Another Engine used to be one of the kinder explanations of BAe.

[MrSkyGuy]

Its a real shame, as the high-wing configuration of the 146 seemed to be a perfect candidate for a 2-engine model, whilst retaining the STOL and relatively-quiet characteristics.

[SeldomFixit]

Didn't our Russian brothers put 2 engines a'top the wings of what was essentially a 146 configuration ? :confused:

[mrmagooo]

The An148.......

Not similar in anyway :eek:, but then the Russians never did copy other peoples designs, did they?

http://en.wikipedia.org/wiki/Antonov_An-148

[SeldomFixit]

The 416 is something of a cryptic, if not dyslexic giveaway :ok:

[GGFFB]

"The 146 was designed for rough/ short strip operations. In addition to the given John Wayne Airport I think its the only jet that can operate out of Jersey (JSY) and until recently London City (LCY)."


Not quite Steve. For a long time it was the only Jet that was scheduled to operate into Guernsey (and still is for that matter) pending the outcome of the BE 195 debate. However BA, LH and Braathens have all operated 737's into there amongst others.

JER on the other hand once had an L1011 in here, although the largest scheduled type at the minute is the 320 (EI,BD,S4).

[MrSkyGuy]

And I didn't see any 146's at KSNA when I was there in 2006. All 757s and 737s.

[NigelOnDraft]

An answer not really explained above...

An engine failure at rotate/V1 loses a 146 25% of thrust, a "126" 50%. If it now needs to climb over an obstruction, the twin will have a large payload penalty, or the twin needs much bigger (and expensive) engines to start off with.

Unfortunately, while there are routes (LCY) where this is/was needed, not enough to base/justify a whole design on...

NoD

[MrSkyGuy]

Its unfortunate, because I firmly believe that the same advantages that the 146's 4-engine configuration have led to the model's relatively recent unpopularity with carriers.

[Nopax,thanx]

An added bonus that got us out of trouble more than once when I worked for TAY was that if you had an engine problem away from base you could fly home (non-revenue) on three.

But of course the real reason was "Not enough room for eight!"




(sorry, had to do it! :E)

[AR1]

Hot & High was the reasons that stick in my mind. I have of course the complete encyclopaedia of Aircraft (in weekly parts) from around the relevant period, that I will consult for the definitive answer.

From one who was there, they were (are) astonishingly quiet.

[MrSkyGuy]

I'd love to hear what you come up with, mate!

[Vortechs Jenerator]

Don't confuse BAE (Or Hawker Sydley) press releases to the industry and advertisement claims against real reasons.

Budget. Budget. Budget.

When the aircraft was fist designed in the late 60's - 70's, the choice of engines that had been through the (lengthy and expensive) certification process was limited.

The Texxtron/Lycoming (then) engine variant had been in helios in vietnam and was based on a older core engine from a tank (although Honeywell think it was a completely different engine).

I don't know why people are mentioning "Hot and High", the ALF 502 is very asthmatic with limited turbine margin on a good day and the later 507 on the RJ is not much better.

I've worked on 146's/Rj's on and off for 12 years and the above is just stuff I've picked up on various courses over the years.

The RJX should have been designed with 2 larger motors IMO, 4 Donkeys on a regional jet did scare people who were awaiting the Embraer 170/190 family coming off the drawing board.

[WOTME?]

The 502's in the first 146's were really unreliable dogs,it was a good job there were four of them(& a good job they're easy to change).
When Allied Signal acquired Textron Lycoming they spent a small fortune on increasing the reliability & these days they're not too bad.
The 507's in the RJ's have the increased temp margin but are still prone to the occasional uncontained failure.

[Golden Rivet]

Why Four Engines?

Easy, the wings weren't long enough for 6.

[MrSkyGuy]

Ayuk ayuk. :D