Typhoon Teething Problems

ROYAL NAVY Sea King HC4 support helicopters are flying in Afghanistan with modified composite rotor blades.

Carson composite blades and a new five-bladed tail rotor allow the helicopter to operate with increased carrying capacity and speed in the demanding conditions of Afghanistan.

US-designed Carson blades were selected following an extensive test and evaluation programme conducted by ATEC (Aircraft Test and Evaluation Centre), part of the UK Joint Test and Evaluation Group

AS THE RAF Typhoon Force, based at RAF Coningsby, Lincolnshire, continues its efforts to expand the type’s capabilities and prepare for its future operational debut, AFM has received details of recurring problems with the jet. These are currently being investigated by the RAF and the aircraft’s manufacturer.

On March 5 last year, the pilots of four Typhoon F2s returning to Coningsby from a routine training sortie were instructed by air traffic control only to lower their undercarriages when they were steady downwind and clear of the surrounding villages. Two months within the UK Ministry of Defence. The work supported an Urgent Operational Requirement (UOR) to enable the Sea Kings to be deployed.

Trials were carried out in ‘hot and high’ conditions in Colorado, followed by operational training by 846 Naval Air Squadron in Cyprus using the first modified Sea King HC4. Hover performance was shown to have increased by 2,0001b (907kg) and forward speed by up to 49 knots (91km).

The £5.25 million upgrade programme lasted ten-months from UOR declaration to delivery later, in early May, the parachute of a Typhoon F2 fell out of its housing on rotation. Thankfully, all the aircraft involved in both these incidents landed safely. On November 1 last year, a Typhoon FGR4 suffered nose wheel steering problems which forced the pilot to abort his mission.

Even before these incidents, AFM had become aware of ongoing problems involving the Typhoon, not only with the undercarriage and ‘chute, but also with the fuel system, which has been causing centre of gravity (C of G) limit warnings in flight.

AFM has since learnt, from approaching the Typhoon Integrated Project Team (IPT), that problems involving the aircraft’s undercarriage, parachute and fuel system have still to be rectified.

A statement from the team said: «We expect that an aircraft of Typhoon’s complexity will encounter technical issues throughout its working life. This working life has so far seen in excess of 17,000 hours flown by the RAF Typhoon pilots. While these issues are important for us to resolve, the fact remains that there has been minimal impact to the effectiveness of Typhoon.

«These issues have been investigated and we have taken all necessary steps to minimise any risk to our crews, the public and property, which is paramount.» IPT supplied AFM with the following information about the ongoing investigations.

Firstly, it said, in respect of the undercarriage, on occasion the nose landing gear does not retract because of a fail-safe feature to prevent inadvertent damage should the nose landing gear not be correctly aligned for retraction. It advised that speculation on the cause of the incidents before the engineering investigation has concluded would be inappropriate.

«This has been a difficult technical issue to resolve,» it said, «because of the infrequency of occurrence and the fact that we cannot replicate the actual aerodynamic loads on the ground.» At this time, says Typhoon IPT there is no operational impact and when the nose wheel landing gear does not retract, the undercarriage remains in position to allow the aircraft to land safely. Work is underway in conjunction with industry to resolve the issue.

Secondly, it adds: «The locking mechanism for the nose wheel door has occasionally failed to unlatch correctly, resulting in damage to the component as the door has been opened during the undercarriage lowering sequence.» This issue has also proved difficult to resolve, again because of the inability to replicate aerodynamic loads on the ground.

A technical procedure will be implemented over the coming months to address the primary cause.

«Issues with the brake parachute deployment and door mechanisms have resulted in a number of incidents where the chute does not deploy satisfactorily,» says Typhoon IPT.

However, it adds, all incidents involving the chute have been contained, and a revised aircraft operating procedure is now in use to minimise the risk of recurrence and to ensure the continued safety of pilots and the public. The aircraft has a wheel brake system and aerodynamic Gift dump) that provide safe braking.

A joint engineering investigation between the RAF and the aircraft’s manufacturer has developed a solution, which will be applied to all aircraft in service and those on the production line.

Finally, in respect to C of G issues, the pilot is currently receiving too many warnings, showing that the aircraft C of G has moved to a warning limit position.

«This is a complex technical matter that is taking time to resolve, partly because of how the fuel system and flight control system work together,» says IPT. A major part of the ‘fix’ requires accurate fuel gauging, achieved by modifying software. This is being implemented, and the result will be applied to all aircraft in service and on the production line.

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