Once upon a time there was a Shackleton Mk3 phase 3 on detachment from Ballykelly to Akrotiri. The time had come to return home, the long flight planned to take three days with night stops at Luqa and Gibraltar.
Sunday, and the aircraft was loaded up with the belongings of the ten crew members and nine ground-crew/passengers. The Squadron packup and some of the luggage was loaded into two (Unjettisonable) panniers in the bomb bay. As it was only two weeks to Christmas. we had lots of sacks of fruit which, with the rest of the luggage, was loaded into the nose of the aircraft. (The Mk 3 Shack was very tail heavy and all the extra weight had to be loaded forward of the C of G)
Monday, Akrotiri to Luqa. Four hours 40 minutes at 1000ft - Uneventful.
Tuesday, Luqa to Gibraltar. Six hours - Flew through a severe sandstorm for one hour.
Wednesday December 13, 1967. Early morning, looking forward to getting home after six weeks away, arrived at the aircraft to be met by the crew chief who says they have accidentally overfuelled us - would it be ok? Quick check of the ODM for take-off distance etc and decision made to accept it. 3500lbs above planned TOW. Eventually got airborne from Gib for our planned nine hours 30 minute flight to Ballykelly. Some two and a half hours into the flight, vibration was felt through the aircraft and the airspeed fell by about 20kts. A check of all powerplants showed that No 1 engine's propeller translation unit had failed and ball-bearings and sparks were flying off it as it broke up. This failure meant that we had lost control of the rear prop, which under CTM, had gone gone fully fine, and the front prop had coarsened off to compensate. The engine was shut down and the front prop feathered, but it continued to windmill slowly. We were now 90 miles NW of Lisbon so, after a Pan call had been made, we informed Lisbon that we were diverting there. Wing tip fuel was jettisoned (3600lbs), and the aircraft was turned towards Lisbon. The vipers prepared for immediate start up and fuel jettison was started from the main tanks.
A few minutes later, 17 minutes after the TU failure, the signaller in the starboard beam lookout position called the flight engineer to report oil leaking from around the jet pipe of the starboard viper. The eng went back and confirmed that it was oil leaking from the No 4 Griffon. The leak rate rapidly increasing and the captain was informed that No 4 would have to be shut down. It was obvious that the engine was 'gulping' but, instead of oil coming out of the normal vent pipe, it was pouring out of the cowlings and going straight down the intake of the starboard viper.
The imminent loss of a second Griffon meant that the vipers would have to be lit up, so fuel jettison was stopped. (The vipers ran on Avgas and it was banned to jettison fuel and run vipers at the same time because of the fire risk) The starboard viper would not light up- no big surprise seeing 30 gallons of Griffon oil had gone through it- but the port viper was started before No 4 was shut down and its prop feathered.
A mayday call was transmitted and, with take-off power on both inboards and the port viper at 100%, the aircraft stabilised at 500ft and 150kts. We decided not to attempt a further start on the starboard viper because it was soaked in oil and fuel from the first attempted light up and the fire risk was too great. A further consideration was that we couldn't afford the extra drag from the open intake door for the 40 secs or so it would take to try and start it.
Nursing the aircraft along and running the viper for periods of between 5 and 10 minutes with one minutes rest, we could just manage very shallow turns but, even in these the airspeed fell to a perilous 140kts. Trying to rest the Griffons by throttling them back from 2750rpm caused an instant loss of speed so that they were kept at take-off power throughout.
By the time permission was given by ATC for a direct approach to runway 03, we were hugging the coastline at the entrance to Lisbon harbour and having to map-read our way to the airfield because the ADF was u/s and there was no radar available. Visibility had dropped to one-and-a half miles in the smoke haze from the city and 'it was with some surprise' that we saw the Salazar Bridge directly ahead and above us! (Because of it's recent construction it wasn't on our charts!)
As we could not fly beneath the bridge and we hadn't got the power to climb over it, we turned away and flew down the estuary in a desperate but unsuccessful attempt to gain height. At this stage the Captain of a Portuguese Boeing 727 belonging to TAP heard on R/T our predicament and offered his assistance. He then closed in, reduced his speed to match our 140kts, and led the way across the outskirts of the city to the airfield. Fortunately, thermal uplift as we coasted in gave us a valuable 400ft increase in altitude so we were now 900ft amsl but still only 500agl!
At 2 miles the runway became visible and we informed the 727 captain that we were visual. The 727 was dead ahead and at the same height as us as the Portuguese captain selected power for his overshoot, the consequent turbulence made the poor old Shack perform aerobatics and the airspeed fluctuated down to 90kts.
The eventual touchdown was made at 120kts and 26 minutes after the failure of the second Griffon. The aircraft captain, the late Flt Lt Bondesio was awarded a well earned AFC.
As a direct result of this incident, trials were carried out and the aircraft was cleared to jettison fuel with the vipers running. The viper controls were modified so that variable power settings were available instead of only full power or idle. The handling SOP's were also changed so that if a Griffon engine failed, both vipers would be started and run at idle power available if required. This meant, somewhat humorously, that when the four-engined Shack lost and engine, it subsequently ran on five!
Original article written by MEng Roy Craig and published in the 'Air Engineer' magazine 1989