RAF and Single Engined Fighters

[Razor61]

The Gripen thread got me thinking as to why in the last 30 years the RAF (or MoD for that matter) have not chosen any single engined interceptor/attack aircraft and have kept with the two engine design.
Bucanneer
Phantom
Lightning
Tornado
Typhoon
Sea Vixen
Etc

Alright we have a few examples such as Vampire, Venom, Hunter and Harrier (and the F-35) but the trend seems to be put towards the two engine layout.

Why is this? Has this been a decision maker in future programmes also as to why we haven't gone for Gripen or the F-16?

[XL319]

Jet Provost, Hawk and Harrier is the only two jet planes i can think of.

[Gainesy]

Survivability, when one engine goes TU, the second gets the aircraft to the crash site.

[OCCWMF]

XL319 - I make that 3.

[Eagle402]

XL319 - Harrier has a single Pegasus engine.

[ORAC]

Folland Gnat

[Razor61]

In regards to the listed aircraft with single engine, i was talking about front liners (intercept and attack).
The Gnat etc were not front liners.
The Hawk in the UK can augment the Interceptor force and to an extent attack force but they are not front line (although they are used for front line in other countries)

I understand the survivability issue so why do countries still develop single engined interceptors and attack aircraft (F-16, Gripen etc) when the chances of banging out and losing a jet due to engine faliure are obviously much higher than that of a two jet plane.

Surely the cost of the jet being developed doesn't out weigh the fact that when they start falling from the sky with an engine out then it starts getting rather expensive also.

[airborne_artist]

How many instances are there of twin-engined military combat aircraft landing with one engine shut down and the other fully serviceable? I guess it's not in the public domain, but I doubt there are many.

[WhiteOvies]

Deliverance,
Each engine type has different tolerances depending on the design of the blades on the inside. FOD is still the No 1 ECU killer across all types although some are more prone than others - Harrier is a hoover, and the F16 has issues as it's intake is so close to the ground. From an engioneering perspective its down to how quickly the engine can be replaced to make the jet flyable again. The Harrier is awkward as you have to take the entire wing off whereas I beleive an F16 can have an engine replaced in about an hour(it just slides out and back in). Tornados have issues with water collecting in the intakes and then 'soft' fodding the engines. Its unusual that one intake be dried out but not the other, hence leading to a double rejection.
Once in the air birdstrike is probably your biggest issue, such as the Tornado that went down over the Wash last year. In a single ECU jet one big bird will do it (Indian Harrier 2 seater went down to a barn owl last year) at least a 2 ECU jet has a chance, but birds tend to flock and sometimes it just isn't your day.

[GOLF_BRAVO_ZULU]

XL319. Was your intention; Jet Provost, Hawk and Harrier are the only non two jet planes I can think of?

Leaving aside the peace time flying, 2 donks are rather handy insurance should the opposition throw HE or metal at you. That said, they are so close to each other these days, they'd probably suffer sympathetic damage anyway.

[ORAC]

First lets discount the remark concerning the last 30 years. The Tornado, F16, F18, F18 etc were all initially designed back in the 70s - if not the late 60s.

Early jet engines were weak so a single engined fighter (Vampire, Sea Hawk, A-4 etc) had to be relatively small, light weight and short range. No real problem for short-range agile IDF or FBA aircraft, but longer range aircraft needed 2 engines.

Early engines were also unreliable so single engined aircraft were lost a far higher rate, the expense of having and running 2 engines was offset by not losing so many. It also helped that, over the ocean, you tended to get the crew back - which is why the RN and USN liked them. Which explains the Buccaneer, F-4, F-14, A-6, A-5 etc.

Engine power improved, as did reliability. The F-16/F-18 fly-off probably marked the point where the improvement made the loss rate etc acceptable - at least over land. Hence the USAF going for the F-16 and the USN for the F-18.

At the top end where you want high performance the thrust of two engines still win. Which is why the Typhoon, Rafale, F-22, SU-30 etc have two. For bomb trucks where, apart from TO and landing, you want low fuel burn, a single engine will probably now win out, though I don't know anyone building one apart from the Gripen.

I say that because the F-35 design is driven by the STOVL requirement which pretty much ruled out two engines from the start.

I am surprised the Russians haven't built a NG Mig-23/27 replacement. There must be a market for it.

[dakkg651]

ORAC

Early engines were also unreliable so single engined aircraft were lost a far higher rate, the expense of having and running 2 engines was offset by not losing so many.

I think the Meteor was the exception here.

In the 50s and 60s it was easy to acquire your own meatbox.

You just bought an acre of land and waited!

[Pontius Navigator]

the expense of having and running 2 engines was offset by not losing so many.

I think the Meteor was the exception here.

In the 50s and 60s it was easy to acquire your own meatbox.

dakkg, you didn't mention why.

'twas not because they had twice as many unservieacble engines, it was that wonderful logic that said, we are likely to lose one engine so we must practise flying on just one.

And lo, they did and the twin-engined aircraft one one engine behaved just like single engined aircraft - they too crashed.

It wasn't just jets. A Valetta, on a check ride, IIRC a good engine was shut down at the same time as the other failed or the drills were executed on the wrong engine.

Same with the Vulcan. If we lose one we will probably lose 2 so we will practise on 2. And lo, they crashed too :(

[ORAC]

And C-130...

September 10, 1973: An RAF C-130K, XV198, c.n. 4219, from 48 Sqn crashed at RAF Colerne in Wiltshire. It was carrying out co-pilot training when it was overshooting from runway 07 with a simulated engine failure when the other engine on that side failed. At that height (400ft) and speed involved, the asymmetric forces proved too much for the crew to control and the aircraft dived into the ground. The Captain was Sqn/Ldr Tony Barrett, and all 5 crew died.

[mr fish]

er, going off on a tangent here but the US navy don't ( or didn't ) have a twin engine bias, crusader-corsair-skyhawk, and now f35. seems a lot more s:mad:t hits the fan over water, or something!!!

[EyesFront]

There have been plenty of single engine fast jets with more than adequate performance, but the UK has certainly tended to go for twins, since the Hunter

Mirage III & 2000
Etendard
Corsair
Crusader
Viggen
Draken
Skyhawk
F104
F102 & F106
G91
F16
Gripen
etc...

Curious that fast jet trainers (apart from AlphaJet) all seem to be singles. Maybe they follow Lindbergh's logic that two engines just doubles the probability of an engine failure....

[Finrider]

Concerning in flight shut downs, I've had 3 in 1000hrs on the Tornado, 2 Oil Ps and a mech fail (gearbox driven by HP shaft disintegrated). Both Oil Ps were a long way from a div so that would have been 3 ac lost! I may just have a heavy left hand...but they were all in the cruise at well below max cont.

[ORAC]

Curious that fast jet trainers (apart from AlphaJet) all seem to be singles. T-37 tweet, T-38 Talon, Aermacchi M-346.

[misd-agin]

T-37 fast jet trainer? Hahahahhahahahahha

[XL319]

yes thanks for the correction. I did get my words mixed up. ONLY THREE JETS was what i meant. Thanks :8

[Wingswinger]

Well, during my time on FJs I had two engine shut-downs/failures on twin-engined aircraft (Tornado) and two on single-engined aircraft (Hunter). Only one MB tie. :}

[fake wafu]

It's an interesting question. The Tornado GR1/GR4 having been in service for over 25 years I would think that the number of real single engine landings is not trivial. My experience is in line with fin's although more failures (due to more flying hours :} ). I wonder if any ginger beers have a view on this...

[TalkTorqueTorc]

I would say that there are maybe two or three single engine landings a month at least.

One thing to bear in mind though is that if you have two engines and you have a problem indication on one of them you can do a single engine approach and not risk using a potentially dodgy engine.

On Tornado a large number of single engine approaches were for transitory engine vibration which on further investigation turned out to be the detection system inducing a signal and not a problem with the engine at all. Lots of single engine approaches when not required but would you want to take the risk of an engine failing on you at a critical time?

Happy to say the system was modified so the number of spurious VIB captions has dropped.

[Lima Juliet]

I lost one of 2 donks just 25miles South of Baghdad when the locals on the ground weren't friendly (not a brown-job pongo for miles).

Happy with 2 engines that day as I limped into Kuwait.

QED?:ok:

[LowObservable]

Twin engines cost rather more for equivalent size, and design around the a:mad: end of the aircraft is trickier.
Most twin-jet fighters - the Jaguar and F-5 are exceptions - are twins because there was no fighter engine big enough to do the mission with a single when they were designed. (Even the classic Bug had 32k thrust at service entry, much more than any modern fighter engine of the day.)
Dave is a single because it's STOVL. Making it a twin would have been insanely complicated. Also, unless you can sort out the asymmetric issues in powered lift, an engine problem in STO or VL is more dangerous with a twin than with a single (because it will turn upside down very fast) and with two engines it is twice as likely. Very early on, the Navy wanted their version with two F414s, but "studies" were done which "proved" one engine was just as good.