A Sentry aircraft damaged in a storm will soon be back in service after a two-year repair programme involving 25 miles (40km) of replacement electrical cable and more than 2,200 new parts.
One of the RAF’s vital fleet of Airborne Warning and Control System (AWACS) aircraft is due back in the air this autumn after surviving a runway collision and – during its structural repair – an earthquake.
The RAF Waddington E-3D Sentry aircraft was struck by a towing aid during a storm two-and-a-half years ago. Since then a team led by Northrop Grumman including its industrial partners, the RAF and Defence Equipment and Support’s (DE&S’s) Sentry team – which provides maintenance for the seven-strong fleet – has been working round the clock to get the aircraft back into service.
The damage occurred on 18 January 2007 when high winds at the Lincolnshire base ripped a towing aid from its moorings causing it to embed itself in the side of Sentry ZH106 while it was parked on the pan.
Keith Monslow, the Joint Sentry Support team’s operations manager, said:
“It was the worst possible place to strike the aircraft – in the fuel gallery. The whole area was covered in fuel, which soaked right the way through to the lower lobe, contaminating the electrics.
“Opening up the aircraft to inspect the damage just made it worse. Fuel covered all the electrical areas. And some of the items needed in the repair aren’t even made any more so we knew we would be hunting all over the world for places to fabricate them.”
Externally the aircraft needed a comprehensive structural rebuild including new skins and frames to replace those crushed in the collision. Staff from Forward Support (Fixed Wing) from RAF St Athan were enlisted to do the work which was completed in the first four months of the repair from October 2007.
Having been de-fuelled, ready for its structural repair, the aircraft then needed to be jacked up using fuselage cradles and wing supports, which were brought in from Northrop Grumman’s Lake Charles facility in the USA.
Stripping out the whole of the inside of the aircraft to access cable runs changed the aircraft’s centre of gravity, challenging the repair crews as they worked on the aircraft while it was on its jacks.
Northrop Grumman Programme Director John Parker said: “The aircraft had to be perfectly balanced to do the work. One slip and we could have significantly damaged it.”
More puzzling to staff was that the aircraft continually moved, often by only tiny amounts. Mr Parker continued: “We were finding that it was shifting overnight. A lot of rain meant water got under the hangar and that could have caused movement. Then outside temperatures would change, which might also have had an effect. But we didn’t really know why.”
And then the earth moved, literally. An earthquake struck the east of England on 2 March 2008 measuring 5.3 on the Richter Scale and centred ten miles (16km) from Waddington. Bizarrely, it seemed to solve the problem of the aircraft’s movement.
Mr Parker said: “In the end the aircraft only became completely stable after the earthquake. We think now that it was the pre-quake tremors causing the movement. There was very limited movement after that.”
Miles of cable and around 2,200 new parts have since been installed as part of the repair, including multiple electrical connectors distributed around the whole aircraft.
Once the £3.5m repairs had been completed, the recovery phase began, testing all the aircraft’s systems. On an aircraft which had been dormant for more than two years, it was a delicate process. All electrical protection devices were tested and, when power was stable, full functional testing of all aircraft systems was successfully carried out. Fuel was then pumped into the tanks and the engines fired up perfectly. Finally, the mission system and radar systems were successfully tested.
For the team it has been a remarkable success. With other aircraft from the seven-strong Sentry fleet needing maintenance at the same time the team was kept extremely busy.
Mr Monslow said: “We have replaced 25 miles (40km) of cable from front to back, wing tip to wing tip. The whole aircraft had to be gutted to replace the wiring. It’s one of the most challenging jobs we have ever done, a fantastic effort and a real feat to complete it. It is a true capability demonstration of what can be done.”
Mr Parker added: “The DE&S team said it was a chance to show how we could step up and demonstrate our capability. There is not a part of the aircraft which hasn’t been significantly impacted to accomplish this repair. So if we ever get into a situation like this again this repair clearly shows we have the capability for this level of maintenance.
“And there is no ‘us and them’ with our colleagues on this team; collectively we stand and fall as ‘Team Sentry’. It’s a clear demonstration of the partnering ethos and delivers best value to the taxpayer. We will be excited to see the aircraft go back to the fleet.”
Sandy McGregor, leader of DE&S’s Sentry team, added: “The return of ZH106 to Air Command marks a highly significant and successful event for the Sentry team and Northrop Grumman. It is an outstanding example of DE&S, RAF and industry working as partners to deliver the aircraft within budget, on time and fully serviceable.
“Throughout the last two years the whole team has shown flexibility, professionalism and a relentless ‘can do’ attitude. Everyone associated with this repair should be proud of their contribution to the overall achievement.”
The work of the 160-strong Joint Sentry Support team demonstrates the value of combining a wide range of skills in one place. Paul Screen, of DE&S’s Sentry team, who heads the joint management team at Waddington, said:
“There have been some big wins here on the 106 project. Teamwork and partnering are essential. We have got into some very heated discussions at times but it’s all come up with some very satisfactory results.
“When we started the repair I thought it was going to be very expensive but we have had good value for money, which means the taxpayer has got a good deal too.”
Sentry maintenance is covered by the aircraft’s whole life support programme, introduced by a contract between the Sentry team of the former Defence Logistics Organisation and Northrop Grumman in 2005 to support the fleet until it’s out of service date, currently 2025.
Northrop Grumman leads the team which delivers maintenance, support chain management, engineering support, technical data management, software development, aircraft structural integrity and maintenance training.
