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View Full Version : BAe146 - Why not a twin?


paulo
21st Apr 2003, 19:38
I've often wondered...

With twins 'ETOPSing' transatlantic, what's the thinking behind four engines, esp on something so small? Sounds like more build cost & maintenence to me (not that I'd actually know)... only upside I can think of is better stability in asymetric.

Golden Rivet
21st Apr 2003, 19:42
reminds me of a joke -

why has the 146 got 4 engines

- because the wing was'nt long enough for 6.

GR

Jetstream Rider
21st Apr 2003, 20:01
What most people overlook is that the 146 was built for airports that have obstacles on climb out or short strips and so on (true 'regional' airports such as LCY etc). Four engines are so that it can maintain the performance required or better after an engine failure. That is also the reason it is a bit slow and has a low ceiling. You can't have everything and the compromise with the 146 is on the short strip side of things rather than than the fast and high side of things. The maintenance required on 4 instead of 2 engines is just another case of the compromise between performance and costs. Also, it is quieter. Jet noise is a lot higher if the jet eflux is faster (ie the difference between the still air and the jet is high). If you can slow the air down (4 slow streams of air as opposed to 2 high speed streams), you will have a much quieter aircraft that can operate into city type airports with less complaints.

The job it is designed for it does very well - quite a few pilots complain about certain aspects of the 146, but I hear it is very easy to fly and it certainly does the job it was designed for well.

J-R

My names Turkish
21st Apr 2003, 20:14
Good question, often wondered the same myself.

The thing that keeps me awake at night is how anyone can justify the expense. On one of the threads about the Ryanair takeover of Buzz, someone said that the monthly lease of the 146 was TWICE that of the 737. If it takes less Pax and costs twiceas much not to mention the additional running costs how did they ever think they could make money. I suppose that was why they got in the trouble they did?

rwm
21st Apr 2003, 20:50
On course I was told that you could fly the 146 with three engines without missing a revenue flight. I once went to pick one up and we flew home without flaps and only three engines. Also a very rugged machine. Built like a brick outhouse.

Reminds me of a joke too.

Q: What does BAE stand for?
A: Bring another engine.

ETOPS
21st Apr 2003, 23:53
If you look back to the 1970's the original concept for the aircraft was done by Hawker Siddeley at Hatfield hence the type designation HS-146. This followed on from their earlier 3 engined type HS-121 Trident (Sorry to use the T word!). At the time there were no power plants of sufficient thrust that were light enough or quiet enough. Imagine a couple of Spey's roaring into LCY!! So a newly developed mini fan jet was used, but they had to fit 4 to get enough puff.
As the market was not yet mature enough the project was put on hold for a few years until Bae was created so when launched the aircraft became the BAe 146. It only became an Avro when production was moved to the Lancaster factory at Woodford (WFD)
When Avro's planned the upgrade to RJX they did produce some twin engined studies but I'm pretty certain none flew....

spekesoftly
22nd Apr 2003, 02:03
Think I'm right in saying that the 146 was originally a De Havilland design, that was shelved and re-activated several times, throughout the changes from DH to HSA to BAe.

allthatglitters
22nd Apr 2003, 04:19
5 APU's, built in overtime generators, what a machine, sorely missed.

Waldo
22nd Apr 2003, 05:50
Back in my early days of training(late seventies)I seem to remember seeing a model of an aircraft very similar to the 146 with just TWO engines in RAF colours. Maybe it was considered by the RAF but changed to four engines at a later date when no suitable power plants could be found?

Onan the Clumsy
23rd Apr 2003, 00:02
On course I was told that you could fly the 146 with three engines without missing a revenue flight.

Just to clarify: That would be three WORKING engines right?

:}

rwm
23rd Apr 2003, 01:51
To: Bral
I went to recover the machine fro Churchill, and what I remember was we had an asymetry problem and the flaps locked up and the original problem was with the engine makeing metal. So we flew the machine back home, the lease we had planed for it fell through and it went to another operator.

To: Onan
That's what they said. I never operated the type. Just worked 3rd party overhaul on them.

Eagles Forever
23rd Apr 2003, 04:04
spekesoftly

I think the 146 design concept goes right back to a Handley Page project!

RRAAMJET
23rd Apr 2003, 05:52
The "Fisher-Price Starlifter" is indeed a nice aircraft to fly...

It was launched in Aug '73 as the HS-146; originally started life as a D.H. development project - the DH 123.

I believe at one time it was slated to have RR-M.45 501 fans, as on the VFW614 (7700lbs thrust), but they'd gone by the time BAe resurrected the project in '78. Hence the 4 weed-whacker motors...

A two -engine version was looked at in the '80's - no development money, and Textron worked hard to improve the 507's and cover extra maintenance costs over a CFM twin.

Cheers... :8

RRAAMJET
23rd Apr 2003, 10:49
Bral:

Have done a few 3-engine ferries in the -100....none in the -200/300.

One was a similar situation to rwm, the engine chip detector looked like a shaving brush...We took off on 4 (unfortunately, full pwr was required as it was a poor-quality gravelly short strip), immediately shut the sickie down when safely airborne, and flew across the Andes on a good-wx day to SCL for an engine change with the assistance of LAN-Chile. All perfectly safe; the -100 had bags of extra poke. 2-eng stab height was OK to get us through the mountains if necessary, or onto escape routes. And that was Royal...no other choices to keep the mission going...no other way of getting a spare engine to us.

As to flapless: yes, done those, too, and eng-out for practice but only on low-overshoots or rollers, never on T/O. The 146 wing is actually a higher min-speed airfoil clean at average weights than some other much bigger jets I've flown. The first flap position (18? my memory fails me) is a lot of mechanical whirring and whining out-there....those who've flown it will attest to the massive trim change on flap extention/retraction. I seem to remember some pretty high approach speeds flapless, whereas many other jets may still have slats available in a FLAPLESS situation.

And as to Yellow-system failure requiring a chicane-wrist-flick to deploy the roll-spoilers symmetrically...it's British and it works...

Churchill....been there...one must have an intense dislike for polar-bears to be desperate enough to depart no-flap/eng-out...yikes! Hope it wasn't a -300...maybe you mean Ch. Falls?:uhoh: :\

Evanelpus
23rd Apr 2003, 16:15
I can remember when the USAF were closely considering the 146 as a transporter aircraft. The demonstrator (STRA) aircraft was closely studied by their numerous experts. In the end they declined but look what came out of it............. C17!! I am convinced the basic design layout for the 146 was the basis of that aircrafts design.

PAXboy
23rd Apr 2003, 22:55
RRAAMJETa chicane-wrist-flick to deploy the roll-spoilers symmetrically...it's British and it works... Uumm, this sounds like you are saying there is a stand-by system that:

In the even of losing most hyd. power, you can extend two spoilers to lose speed/height. These are retained in the wing by a latch that is released by a specific movement that is not a part of normal handling. Specifically, to flick the (say) port wing high and immediately low and then return to level?

It does sound very British and dashed ingenious! :)

White Knight
24th Apr 2003, 00:30
I flew the more "modern" Avro RJ100 for 2 years - what a lovely aeroplane to pole....Yes, only did M0.70, but it was comfortable to spend 3 hour sectors in. Loads of head and legroom.
Four engines for short airfields - that is the WHOLE point of the 146. Lose an engine and it still goes up at a decent rate. Only decent size jet into places like London City. I'm sorry but you can't call the Embraer Barbie things real size jets, or the canadian thingy.
:p :p :p

RRAAMJET
24th Apr 2003, 00:41
PAXboy:

to explain the roll-spoiler thingy:
(bare in mind this is from nearly 2 decades ago, so my memory is under severe stress here!)

When operating with a complete loss of yellow system hydraulics, on approach it was recommended that, in order to prevent assym. spoiler float, the roll spoilers be deliberately fully deployed by a short application of full aileron in either direction. There is no hyd. pressure involved - they are unlocked by wheel position (10degrees?) and aerodynamic pressure deploys them to full up. That way you know what position they are in; no suprises on finals. From having flown in close formation and watching as it was done into Chester, believe me, it works. :ooh:

Don't know if that's still the procedure, or if it was just our military way of doing things (although it's in one of my airline QRH's as well), but better the Devil you know, as it were....

Help me out, those of you still flying the 1-fuselage4-engines6-wheels.... :uhoh:

RRAAMJET
24th Apr 2003, 12:02
Thank you, Bral....I get muddled easily, these days....can't remember handwheel angles so much anymore! Nowadays in the 777 I just send a telephone call to some flt-control elves in the electronics bay by way of the wheel and various thingies move by magic. Unless the elves have croaked, in which case secondary elves-in-training are backed-up by direct-elves who, if they all croak, leave me praying with a 146-ish cable connected to spoilers 4&11 and a stab-trim elf also on a cable....hmmmmm

We used to practice it at Benson for real, by turning off the main and AC pump, just to get used to the feel - flew fine, sloppy, as you say. :ok:

TopBunk
24th Apr 2003, 12:48
Re 3 engine/flapless

If the runway is long enough wouldn't 3 eng flapless give you better second stage performance, and with the higher IAS give you more controlability wrt Vmca?

Performance never my strong point so expecting to be shot down;)

john_tullamarine
25th Apr 2003, 14:58
Head scratching time ...

There was a quite lengthy paper on the 146's history in the RAeS Journal some years ago and, if I can locate my file copy, I will post the specific issue details for those who might be interested in chasing a copy down for review.

If memory serves me correctly, that paper indicated that the original design was, indeed, for two motors but the particular design engine never saw the light of day and the project, as a consequence, was shelved. Some years later, with the introduction of the smaller US engine, the project was resurrected as a four motor exercise.

PAXboy
25th Apr 2003, 18:01
Thanks for a most interesting discussion and one of the first wholly positive ones on the 146.

Having always liked the machine (from pax perspective) I have never understood it's detractors, save for the concerns about the air intakes and the cooling(?) fluid smell.

One of the things that struck me about the a/c when I first saw it (both in pictures and in real life) - it looks 'right'. Sure it is way off beam from any other design but it looked like it would work?

This is not the place to have another thread of 'most beautiful a/c' but the 146 just looks like it will do what it says on the tin! I realise, of course, that appearance is not the way to buy a/c but the 146 has always had my vote. For the short haul / high load / restricted field, it seems to have it all.

In the newer twins from Bombardier and Embraer and Dornier, is there anything else that can pick up that pax load, get them in and out of LCY (+ similar) and stay as quiet?

TASI
25th Apr 2003, 18:50
Yes it's a nice aeroplane that 146, but it's even better to fly in it than to talk about it.
I have a type rating for the A/C, but no job!
Does anyone have some good tips for me to find one?
Thanks.
:cool:

18greens
25th Apr 2003, 21:49
Everyone talks about the low powered engines. How low powered were/are they? 5000lb?


Also when you talk about the flicky thing to get the spoilers out , can you get them back in again or are they out for good?

Very interesting thread.

steamchicken
26th Apr 2003, 00:05
And what other civil jet would take off from Rraamjet's gravelly short strip, shut down a donk, and then fly over the Alps - pity British Wasteofspace aren't making any more RJs (the last British designed airliner..)

superspotter
26th Apr 2003, 05:50
The really really sad thing though is that Bae didnt have the foresight to carry on with the RJX and now we have a constant reminder up at MANchester airport on the viewing park, an almost brand new RJX sat there, complete with the new Honeywell engines goint to rot...........:{

Speedbird48
26th Apr 2003, 21:36
There was a proposed twin engine version and that was around at the time BAE were trying to sell the project to Taiwan. There is a two engine model in the Avro museum at Woodford.

I just did my annual sim' ride and that involved a three engine take off with the second engine on the same side failing at just after V1. No big deal, just a lot of rudder. I did not get time to try it flapless but will have a go next time and let you know??

There was one ferried back from a defunct Mexican carrier with the #3 engine removed. The engine fan section was taken off and the engine was in the hold. I have seen pictures of it taking off out of Mexico and over the approach lights at Hagerstown, MD. with the pylon decidedly bare!!

PAXboy
26th Apr 2003, 22:11
I realise, of course, that there will be numerous factors in the decision to stop R&D on the RJX.

However, is it the case that Avro's were innovators in this niche and then got overtaken by the others? They went for the broader market that did not have the approach/climb limits of LCY and similar fields and, consequently, were able to sell more machines with a 'simpler' design spec.?

By the time Avro were ready to make the two-engined version - there were just too many other's in the market?

White Knight
27th Apr 2003, 00:10
18 greens - the RJ100's engines were rated at 7,300 lb's. And yes, with a yellow hydraulic failure once the roll spoilers were fully out after actioning the QRH, they stayed out until the engineers fixed the hydraulic system after landing. Just made the aeroplane a little bit less sensitive in roll but that was all.
GREAT machine. Built like a brick ****house. Flies beautifully. And looks good.:ok: :ok: :ok:

phnuff
28th Apr 2003, 02:48
I have been on a lot of 146's as a passenger and always found them pretty cramped, but then on a short trip to Amsterdam, that wasnt really a problem. I remember a few times seeing a weird fog appearing inside when the engines (I guess) started up. It passed in a few seconds. I have often wondered why and could only come up with warm damp air being cooled by air conditioning (however the air conditioning seemed on before start up because it was much colder inside). I have never seen it in any other aircraft. Can anyone point me at the reason ?