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Central Scrutinizer
13th Apr 2023, 13:39
Hi all,

I recently read about the interesting powerplant configuration of the Hawker Siddeley Trident 3B.

For those who don't know, the Hawker-Siddeley Trident, HS-121, was a British trijet of the 1960s similar in overall configuration to the Boeing 727. The aircraft was equipped with three Rolls-Royce Spey RB163 turbofan engines, each of around 46 to 53 kN of rated thrust (depending on variant). Its last variant, the Trident 3B, featured a fourth RB162 booster engine of 23 kN of thrust which added 5% extra weight to the aircraft but provided an extra 15% thrust on take-off. It was used on demand when needed.

Since there's very little information available on this interesting and odd powerplant configuration, I'd love to hear from anyone who knows more of the Trident 3B. I'm particularly interested in the actual operation of the fourth engine. Was it used only for take-off and then shut down? If so, when exactly was it shut-down? Would it be left on for the whole flight? What about shutting it down during cruise but later relighting to comply with potential go-around climb gradient requirements? What were the normal procedures and limitations? How was the fourth engine controlled in the cockpit: did it have its own lever? was the lever the same as the other three? was it rather more like an "on/off" control? Did the pilots or the flight engineer control it? Was it operated in a similar way to those water injection systems on older turbofans like on the 707 and 747?

Any sort of insight into this feature of the Trident 3B beyond what's available on Wikipedia would be greatly appreciated.

iggy
13th Apr 2023, 13:51
And, above all, where did they place the fourth extra engine in an airplane with that engine configuration??? :ooh:

HOVIS
13th Apr 2023, 14:01
The fourth engine was positioned at the base of the fin above the #2 Spey. It was a mainly, plastic on/off turbojet with a total loss oil system. Needed topping up regularly.
A quick search on PPRUNE reveals multiple threads over the years, this is quite a good one.

https://www.pprune.org/aviation-history-nostalgia/331858-trident-engine-locations.html

sorvad
13th Apr 2023, 17:32
I think Blind Pew is probably your man...he lurks on various forums on here.

Jhieminga
13th Apr 2023, 19:23
And, above all, where did they place the fourth extra engine in an airplane with that engine configuration??? :ooh:
See here:
https://flic.kr/p/2fdpwu5
The no.2 engine is in the fuselage with the 'booster' above it at the base of the fin.

blind pew
13th Apr 2023, 20:25
Not me..whilst I did have a couple of rides up front I avoided the big boys fleet and was long gone when they decided that it was within the abilities of lesser pilots to fly all 4 marks.

tdracer
13th Apr 2023, 21:44
So where is the inlet for the 'booster' engine - does it get the air from the conventional center engine inlet? Of is that an inlet just above the center engine inlet?

Boeing did something different for the 727 for Mexico City - they mounted some JATO bottles in the wheel wells - if they lost an engine during takeoff the JATO bottles would fire to give that extra thrust needed. Testing resulted in some pretty spectacular videos...
Eventually they were able to uprate the JT8D engines enough that they could get rid of the JATO assist.

DaveReidUK
13th Apr 2023, 22:07
So where is the inlet for the 'booster' engine - does it get the air from the conventional center engine inlet? Of is that an inlet just above the center engine inlet?

Neither of the above (the inlet above the No 2 inlet duct is for the APU). The boost engine inlet doors only opened when the engine was operating.

https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/1074x551/t3_6b3e8126aef6d6c81ad507b3ff443b75c09fd986.jpg

stilton
14th Apr 2023, 04:25
So this Trident has five engines

blind pew
14th Apr 2023, 06:38
Since no one has answered re operation iirc
it was started on taxi out and had to be warmed up for around a minute. Then a selection was made on a toggle switch into the take off mode. Once the throttles were opened up on take off then it too developed take off thrust. Think it generally ran for around a minute then cut out.
Might had shut down latest at noise cut back from throttle position.
‘Don’t know anything about cooling period.
Couldn’t be restarted as as mentioned lubricated by total oil loss system like speedway bikes.
Two notable incidents with lack of performance on the 3..one out of Malaga where they diverted into Madrid having lost an engine but didn’t check WAT limits (approach climb)..and were forced into a go around by ATC but continued flying downhill..skipper realised and besides flying down a valley accelerated and cleaned up to get onto the front side of the drag curve.
The second was a night take off out of Malta where they took some approach lights out then flew below 50ft radio altitude with the stick shake going until they were able to accelerate. Whoever put the books together added 1km to the available runway length. Got the jump seat from a skipper who had been a copilot on that flight and said what a fabulous bit of flying he had witnessed.
On the T2 we had water injection.

DaveReidUK
14th Apr 2023, 07:38
So this Trident has five engines

Hmmm. There's a reason they're called APUs and not AEs. :O

That said, I recall that the TriStar's APU (Hamilton Standard ST6) was a thinly-disguised Pratt & Whitney PT6 - an engine I got to know much better in a later life, in its more conventional form.

pax britanica
14th Apr 2023, 10:42
Living close to LHR and being an 'enthusiast' one soon got to know the distinctive noise of the Trident 3 , quite an achivements Tridents were pretty noisy anyway. Looking at the pics in the posts the engines look tiny compared to modern-day turbofans and I am not sure the Spey could really be called a turbofan as there is no separate exit for fan-generated thrust as was the case on the first fan jet 707s .

While on the subject I always wondered how a Caravelle would perform with only one engine since being an early generation jet it must have had a pretty heavy airframe and a hefty four wheel main gear

trident3A
14th Apr 2023, 11:34
Living close to LHR and being an 'enthusiast' one soon got to know the distinctive noise of the Trident 3 , quite an achivements Tridents were pretty noisy anyway. Looking at the pics in the posts the engines look tiny compared to modern-day turbofans and I am not sure the Spey could really be called a turbofan as there is no separate exit for fan-generated thrust as was the case on the first fan jet 707s .

While on the subject I always wondered how a Caravelle would perform with only one engine since being an early generation jet it must have had a pretty heavy airframe and a hefty four wheel main gear

The Tridents made an absolute din coming over, only Concorde was louder

HOVIS
14th Apr 2023, 11:38
Turbofan is a designation for any turbojet with a bypass. The Spey is a low bypass turbofan. The separate exits for cold stream air and core gases are only a design preference. The IAE V2500 and Trent 700? also have common nozzles for the bypass and core exhaust.

dixi188
14th Apr 2023, 12:45
I think the term Turbo Fan is not applicable to the RR Spey, it is a bypass engine. The front 4 or 5 compressor stages feed air into the core HP compressor or down a bypass duct.
A Turbo Fan engine has a single stage fan that feeds some air into the core compressors but most of the air goes down a fan air duct.
The RR Tay was a Fan development of the Spey.

pax britanica
14th Apr 2023, 13:17
Dixi

Thnaks-bypass was the word I was looking for but could not remeber, the exhausts nozzles on the Speys look tiny in the pics on this thread. And I know things take time but as has often been pointed out the Spey didnt seem to have much development potential which would obviously limit the Tridents growth. Had it been able to push out another few thousands of pounds thrust then perhaps the T3 would not only have not needed a fourth engine but might have given the 727 more competition

dixi188
14th Apr 2023, 15:54
The Spey was developed into the Tay which was fitted to the B727s of UPS on the 1990s.
The Fanned Spey, as it was called in the early 1970s, was to be fitted to the BAC1-11-700 but never got off the drawing board.
I don't think a re-engine program for the Trident 3 would have got far as there were structural problems with the wing that limited their life.

Central Scrutinizer
14th Apr 2023, 15:55
I think the term Turbo Fan is not applicable to the RR Spey, it is a bypass engine. The front 4 or 5 compressor stages feed air into the core HP compressor or down a bypass duct.
A Turbo Fan engine has a single stage fan that feeds some air into the core compressors but most of the air goes down a fan air duct.
The RR Tay was a Fan development of the Spey.

It's a low bypass ratio turbofan engine as opposed to a pure turbojet.

In any case, this is just semantics. Does it really matter what we call it as long as we know what it is? Not really...

Central Scrutinizer
14th Apr 2023, 15:57
Since no one has answered re operation iirc
it was started on taxi out and had to be warmed up for around a minute. Then a selection was made on a toggle switch into the take off mode. Once the throttles were opened up on take off then it too developed take off thrust. Think it generally ran for around a minute then cut out.
Might had shut down latest at noise cut back from throttle position.
‘Don’t know anything about cooling period.
Couldn’t be restarted as as mentioned lubricated by total oil loss system like speedway bikes.
Two notable incidents with lack of performance on the 3..one out of Malaga where they diverted into Madrid having lost an engine but didn’t check WAT limits (approach climb)..and were forced into a go around by ATC but continued flying downhill..skipper realised and besides flying down a valley accelerated and cleaned up to get onto the front side of the drag curve.
The second was a night take off out of Malta where they took some approach lights out then flew below 50ft radio altitude with the stick shake going until they were able to accelerate. Whoever put the books together added 1km to the available runway length. Got the jump seat from a skipper who had been a copilot on that flight and said what a fabulous bit of flying he had witnessed.
On the T2 we had water injection.

Very interesting. Thanks a lot for these!

sorvad
14th Apr 2023, 16:00
Not me..whilst I did have a couple of rides up front I avoided the big boys fleet and was long gone when they decided that it was within the abilities of lesser pilots to fly all 4 marks.

Ah my apologies bp

blind pew
14th Apr 2023, 18:28
Sorvad..no probs I left to fly the VC10..a gentleman’s aircraft..no one twigged.

tdracer
14th Apr 2023, 19:07
It's a low bypass ratio turbofan engine as opposed to a pure turbojet.

In any case, this is just semantics. Does it really matter what we call it as long as we know what it is? Not really...

What Central wrote. Most "low bypass" turbofans had multi-stage fans prior to the bypass duct (and fan inlet guide vanes), and routing to a single 'mixed flow' exhaust nozzle is a design choice for the nacelle and has little to do with the engine configuration (every JT8D installation I'm familiar with used a single mixed flow exhaust). This is different from a 'pure jet' where the entire engine flow goes through the burner stage (if not always through the burner itself).
"High bypass" turbofans were the next evolution - the first widely produced example being the JT9D - single stage fan, no inlet guide vanes. Many high bypass turbofans used a mixed flow single exhaust (common on the RB211 engine). In theory, there is a performance advantage to a single mixed flow nozzle, although this tends to be negated by pressure loses in the mixer and the extra weight of the longer exhaust.

Discorde
15th Apr 2023, 01:23
I flew the T3 for a year in the late 1970s. We used the boost maybe 1 in 10 take-offs. From memory:

The engine had a three-position control switch, spring loaded to a central off position. The active modes were FLIGHT IDLE and CLIMB, There was a 5-position thrust gauge: OFF, GROUND IDLE, FLIGHT IDLE, CLIMB, TAKE-OFF. During taxi out the engine was lit by the press of a button and auto-accelerated to GROUND IDLE. Entering the runway for take-off the switch was blipped to FLIGHT IDLE. On opening up the Speys the boost auto-accelerated to TAKE-OFF thrust.

At noise abatement the Speys were retarded to climb thrust and the boost control blipped to CLIMB. At 6000 ft it was shut down by the press of a button.

Once shut down in flight the boost could not be relit (although I believe this shortcoming was rectified in later years) . . . which led indirectly to the infamous Malaga incident - the guys shut down the boost at 6k on climbout after which one of the Speys gave up the ghost, so they diverted to MAD. Instructed by ATC to go around on short final the T-bird wouldn't climb with 1˝ of its 3˝ donks dead & flew a very low level circuit before successfully landing off the next approach. It transpired that the crew were operating outside the WAT limit, although there was no way they could have known that at the time.

The boost engine's reliability was poor. I recall doing ATH to LHR with a u/s boost on a warm day. Boostless, we couldn't lift the required fuel so had to tech stop GVA - highly embarrassing. And a winter OSL to LHR off a slushy runway. Full load of pax but no prob using the boost & contaminated runway perf. Light boost just before entering runway. It works! Blip switch from ground idle to flight idle - still working! Capt opens up Speys - and boost promptly dies. Back to the terminal. Eng sucks his teeth. 'Nah, can't do anything here, boys - you'll have to take it home boostless'. Rework contaminated rwy perf - we can take 40(?) pax. Luckily the cull was done by the ground staff rather than us. So we guiltily left behind a load of disgruntled pax.

stilton
15th Apr 2023, 02:48
Hmmm. There's a reason they're called APUs and not AEs. :O

That said, I recall that the TriStar's APU (Hamilton Standard ST6) was a thinly-disguised Pratt & Whitney PT6 - an engine I got to know much better in a later life, in its more conventional form.


Still an engine, just not used for propulsion !

Pugilistic Animus
15th Apr 2023, 15:17
That's not too bad, in fact, A340s have five APUs :}

dixi188
15th Apr 2023, 19:30
That's not too bad, in fact, A340s have five APUs :}
The BAe 146 has 4 APUs and a Hair Dryer.:)

Speed_Trim_Fail
15th Apr 2023, 20:37
This thread has been a delight, thank you to all who contributed!

condor17
22nd Apr 2023, 14:34
Like Discorde , I went ''Tridexterous'' [ All 3 varieties of T-bird ] for the last 3 of my 12 Trid yrs . By then we were taught about the WAT limit for Hot and High airfields .
GVA ... embarrassing ? Surely not with the best lunch allowance in the network .
Memory is not as good as his , regarding operation , but sounds about right .
Winter ops out of GLA , snow , fog 'darn 'Sarf , so Prestwick div. + 1 hrs holding fuel thought wise ..
Holding point 05 , boost fails to go ! ,,,,, Next 1 hr+ sat there 11000+ HP RPM , burning off excess fuel down to Boostless TO wt. Sorry Paisley for the noise .
Because of the boost position , rudder ht is reduced . Thus does memory say X-wind limit reduced ? Or even less allowed from one side than the other ? [ or was that ATP ?]
CS , sorry original ground school on Trids. was in 1973 , so no KNs . .
Seem to remember ,
T1Cs Spey 511s 11000lb thrust
T2Es and T3Bs Spey 512s [W?] 12000lb thrust . Was [W] water/meth inj.?
Rb162 boost engine , 5000lbs thrust , with plastic fan blades .
Helped deliver T3 G-AWZZ on her final flt to BHX for the fire dept to practice on . Min fuel , full chat And the boost , gave us a sprightly t/o !

PB , all civil transport a/c have to be able to lose one engine on t/o , and make 30' ht.[ 15' on wet rwy ] by the end of the rwy .
DR , memory gone but is a B744 equipped with a PWC double PT-6 APU ? Making her a 6 holer .
Thus T3s were 5 holers !

rgds condor

condor17
22nd Apr 2023, 14:39
PS. Wing Cracks and solutions is another story ..
Plates bolted on under the wings , increasing wt. reducing payload , increased fuel burn .
The very sophisticated flight recorder , was brilliant in persuading the germans that the Frankfurt rwys. were the roughest in Europe .
Several 'G' spikes on t/o and ldg . Thus helping to crack the Trid. wings .

rgds condor .

blind pew
22nd Apr 2023, 17:52
Condor …yes you were correct wrt different crosswind limits but don’t understand the relevance of performance A remark re screen height.
Water..iirc someone put meth in a 1-11 which didn’t end well (it burns).
The WAT limits were always available in the takeoff performance calculation manuals (vol3?) but you had to use a bit of creative thinking to apply them.
Twas only one of my many chats with the ex head of the fuel conservation group (known for his descent wizz wheel) that I realised that contingency fuel was already included in our trip fuel and that, along with alternate fuel, was calculated at max landing weight rather than planned weight. I had always thought how economical our operation was as the fuel score was often positive.
He of BOAC fame also mentioned that they had invested in computers for flight planning whilst our flight planning used letraset, printed a load off, which we had to amend by hand until the batch ran out.
Mind you BOAC did go to a lot of weird and wonderful places further afield than Sauchiehall Street.
rgds ace