Ryanair 737's

[low n' slow]

Hey all
Just saw something curious in a recent "air international". A ryanair 737 with very odd looking engines. Streched and uggly, looked more like old turbojets rather than turbofans. Are all ryanairs 737 equipped with these engines or only just a few?
just curious...
/lns

[EGTE]

All -200 series Boeing 737s look like that. It's not just Ryanair!

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It's hard to soar with the Eagles when you work with Turkeys!

[low n' slow]

Ahh, I see!
I've never quite understood all the boeing series. That makes the -200 an "old" version compared to the -400 or -800, am I right?
When did Boeing start to produce 737 with todays turbo-fan engines?
cheers/lns

[Cyrano]

Low n' Slow,

The Ryanair 737-200s have hushkits fitted to reduce the noise levels (well...it's all relative...to a 1-11, for example... :-) ). I believe the extra section at the back of the engine is part of the hushkit equipment. The engines *are* turbofans, P&W JT8Ds, but have a much lower bypass ratio than the modern CFM56s and similar (hence smaller frontal cross-section, and more noise).

You'll see pictures of other 737-200s (either old pictures, or pictures of aircraft in countries with less-strict noise regulations) which have "shorter" (i.e. standard) engines.

Have a look at
http://www.boeing.com/commercial/737family/index.html
which should answer your questions about 737 series and production dates.

Cheers
Cyrano

[MikeSamuel]

Interesting topic...I've flown Ryanair many times...they are like a local bus service! Always wondered about the engines...Always thought they looked old and dodgy... ;)
Ryanair provide a decent enough service though, hats off to 'em.
Are there any differences in the safety/reliability of these engines as opposed to the regular ones?

Regards

Mike

[???pax]

I remember these "elongated" engines from many of the holiday flights I went on as a nipper.

Are they the ones where you can see the thrust reversers deploy out of the back??

What happens on the modern engine?? Does the thrust reverser work in a similar way with the only diiference being that the passengers can't see what's going on?

[low n' slow]

Cheers Cyrano!
A very informative page there!
What strikes me is that these early JTD8 engines looke very similar to what the MD80-83-90 has. And if we consider noise, these engines are situated alot close to the cabin compared to the 737 (either version). I would have thought it wise to replace these engines with the new high bypass engines. Any thoughts?
What is nice is that the reverse can be very clearly seen on this type of engine -those big plates redirecting (vectored thrust?) the jet. What is less impressive is that especially (my opinion...) the 737 gets a bit of that dodgy and tupolev "aeroflot" look. For customer service, I would as soon as possible get rid of these engines and stick a pair of high bypass things under the wing, but then there's the cost issue!
Thanx for some good answers
Regards/lns

[Cyrano]

Low 'n Slow:

Getting rid of the low-bypass JT8D engines and replacing them with high-bypass CFM56s is basically what Boeing did in going from the 737-200 to the 737-300 (adding a few rows of seats too). I think there were also various system upgrades too, though I don't know whether anyone looked at the idea of retrofitting the new engines to old 737-200s.

And you're right, the MD-80 series also used JT8D engines.

But I didn't quite understand your comment about changing the engines for customer service reasons. (I leave aside the philosophical issue of whether Ryanair and customer service can rightly be mentioned in the same sentence http://www.pprune.org/ubb/NonCGI/tongue.gif ) "Noise levels" doesn't relate to cabin noise but rather to the noise footprint of the aircraft as heard on the ground (after takeoff in particular). Thus it's not a customer service but an environmental issue.

Cheers
Cyrano

[low n' slow]

Ahh, my comment referred to the MD80.
Have you ever sat right back in the last row seats in an MD80 (during flight)? It's a contributing factor to tinnitus! I'm just speculating araound alot of engine related topics here.
But to clarify, there's no reason to change engines on the 737-200 for customer service, as I see it. Mainly because the engine noise does not affect the cabin to the same extent as rear-fitted engines does.
The modern 737 (-800 for example) has very nice systems. They must have been upgraded as they are the latest in display technology. One thing to bear in mind is that it's mainly "display technology". The instruments work just like before. It's more about delivering it all in a nice package!
cheers/lns

[Puritan]

There's an awful lot more to it than just 'bolting-on' a couple of new(er) engines - it just doesn't work that way - i.e. when an aircraft is originally constructed it's done so with a particular engine-fit in mind. To latterly re-engine aircraft, with power-plant which wasn't intended for it, usually involves substantial (read, very expensive) re-working of major structures of the aircraft, e.g. the wing.

There's nothing inherently wrong with the Pratt & Whitney JT8's that are bolted on to B737-200's - they're just noisier than the CFM56 series which you find on the B737-3/4/5/6/7/8/9-00's.

From the safety point of view, all aircraft engines are periodically stripped down to their bare component parts and rebuilt - using new parts where necessary - and so a JT8 engine that's just come out of the engine workshop should be in better condition than a CF56 that's just about to enter the same engine workshop.

The thrust reversers on JT8's are of the 'clam-shell' variety - they actually form part of the jet-pipe, but are hydraulically moved when the flight crew command them into reverse thrust when they want to stop, during which time all of the jet efflux is then directed forwards.

Now due to the high-bypass construction of the CFM56 engines it is not feasible to provide clam-shells. Instead it uses hydraulically actuated 'blocking-doors', located towards the rear of the high-bypass portion of the engine, in conjunction with a translating sleeve (a piece of the rear section of the engine cowling) which slides aft when reverse thrust is actioned from the flight-deck. However, this design only allows the air from the big fan at the front of the engine to be redirected forwards, i.e. there is still a substantial amount of air emanating rearwards from the high pressure turbine located in the centre of the engine.

Accordingly, plus due to the angle (vector) which the jet efflux leaves the engine, reverse thrust is not as effective on the CFM56 as it is on JT8.

Nb. In any case, and dependant upon which level of 'Autobrake' that the flightcrew of a B737 have selected (i.e. Off, 1, 2 or 3, or Max), reverse thrust acts to off-load the brakes yet provide a constant rate of deceleration, i.e. the landing role distance will be the same, but the brakes won't be quite so hot after a stop during which reverse thrust has been used. Of course with Autobrake set to RTO (rejected takeoff) and reverse thrust used as well, you can stop on a veritable sixpence - it's very impressive ! (but doing so comes at the risk of serious problems from the heat generated in the brakes).

Reverse thrust is more effective at higher speeds than it is at lower ones, with caution to its use on slippery runways with cross-winds.

Another idiosyncrasy of the CFM56 engines are that they are located substantially forward of the wing (especially so when compared to the JT8's, which are slung directly beneath the wing - as per the original design for the B737), and this accordingly causes the aircraft to suffer from a large pitch-couple when power settings are changed - but it's something that you get used to when you're flying aeroplanes powered as such.

[low n' slow]

Well that brings closure to this topic!
Sometimes I miss a couple of details, such as the fact that a/c are designed with specific powerplants in mind. I'm not in any way an expert in these engines, I'm just a student and have not yet read any turbine theory. However, I do learn all the time, so bear with my sometimes weird questions, and I will be very grateful as it gives me an oppertunity to stay ahead of ground school!
Cheers for some very good answers!/lns