Chaps
May I make some comments about provisions needed following (total) engine failures in general?.
The Harrier could not be flown without hydraulics for the flying controls so it was fitted with two engine driven HYD pumps plus a RAT driving a third hydraulic pump in case the engine SEIZED in wingborne flight which would instantly kill both EDPs. Thus the RAT would allow you to glide around and organise a controlled ejection in your own time as height allowed.
Bus14 is therefore correct in his post although he did not spell out the seizure bit as the only likely cause of double EDP failure. He is also correct that there was a RAT related servicing and defect rate penalty, first recognised by the USMC who responded by removing the RAT and then the RAF did ditto.
The VITAL difference between the Harrier and the later Hawk is that the Hawk engine would not windmill at normal gliding speed and so you needed to supply hydraulics from a RAT. The Harrier engine has a huge fan to help the HP spool windmill and would probably enable sufficient hydraulic flow from the EDPs alone down to 150 kts, although as Bus said that may have been an academic point in service. It was not so in testing, where Hugh Merewether saved two Kestrel weight aeroplanes and Barrie Tonkinson got a heavy Harrier two seater on to the ground at Boscombe one Saturday morning, all following total engine failure.
Unusually, I am puzzled by BEagle’s comments about the effect of instability on gliding around and landing. The flight controls don’t know whether engines are running only whether they have normal electrics and hydraulics on line, so I do not see why handling would be affected following engine failure.
So the issue for me would be does the Typhoon have such provision for electrics and hydraulics from either a RAT or other emergency power unit (perhaps hydrazine operated for example like on the Israeli Lavi – a similar looking aeroplane to the Typhoon but with one engine) or best of all from engines that windmill at sensible gliding speeds. I suspect there might be a windmilling problem with Typhoon because all these modern twin engine aeroplanes use pretty small diameter donks (as does the Hawk) and so they will necessarily have limited windmilling torques available to drive accessory gearboxes which can absorb literally a hundred or two of HP.
But a lot of good people have worked for many years on the Typhoon so if it cannot glide around following a double flame out then I would be very surprised. A double flame out can be caused by plenty of non engine related issues from n over root theta upwards and downwards so you must be able to cope with such an event for several minutes while you set about restarting those perfectly serviceable donks. Or at least one of them.