As aviation continues its twin engine march, yesterday marked the end of an era for another Trijet with the RAF formally retiring its final two L-1011-500 series TriStars after 30 years of service.

Departing RAF Brize Norton  for a refuelling sortie over the North Sea before one aircraft conducted ceremonial fly pasts to mark the disbandment of the RAF’s 216 Squadron, formed in 1917 and in operation continuously for 97 years. Only 250 TriStars were manufactured by Lockheed, with the nine L1011s that saw service with 216 Squadron previously operated by British Airways and Pan Am joining the RAF in 1984.

Lockheed L-1011 TriStar prototype during its first flight on November 16, 1970. Image: Air Pictorial magazine, January 1971.

The TriStar began as a request from American Airlines for a widebody aircraft that was smaller than the 747, but offered equivalent range and capacity to the recently retired DC-10. The TriStar was a technical marvel in many areas incorporating aerodynamic, avionics, engine technology and a cabin design that surpassed the market offerings of Boeing and McDonnell Douglas.

Mounted into the rear fuselage, the middle engine was fed by an S-duct (similar to the B727) rather than adopting the DC-10’s separated vertical stabiliser mounted engine. The design reduced airframe drag and improved stability.

In the cockpit the L1011 pioneered a number of important technological advances, being the first widebody to incorporate:

  • an Inertial Navigation System which aligned the aircraft’s navigation system using current latitude and longitude;
  • an advanced autopilot system with truly independent autoland capability, fully certified to FAA CAT-IIIC zero visibility conditions;
  • automated descent control or Direct Lift Control (DLC), allowing the aircraft to maintain a consistent pitch without the need for pilot input by using four redundant hydraulic systems to automatically deploy spoiler panels to maintain the selected angle.

The sole engine choice was Rolls Royce’s groundbreaking triple-spool RB211 turbofans offering an unprecedented advance in engine technology. It was the first engine to incorporate carbon-fibre fan blades that delivered fuel efficiency and a power-to-weight ratio better than any competing design. Ironically the turbofan that launched RR into a global leader in aircraft engines was also the L1011’s downfall – design issues delayed the engines entry into service (EIS) by two years to 1972. The delay gave GE an advantage, it delivered its higher-thrust CF6 engine facilitating an earlier EIS of the intercontinental DC-10-30, highlighting the inherent inflexibilities in the L1011 design, which also suffered from a higher than expected MTOW and centre of gravity issues limiting its payload.

Image: Allan Huse

Teething issues overcome, the L1011 demonstrated reliability and redundancy in an era of that saw an increasing number of challenging aircraft accidents. Eastern, and later Delta were the largest US operators, while Cathay Pacific operated the largest L1011 fleet outside the US with 21 aircraft flying across its pan-Asian network.

But Lockheed needed to sell 500 aircraft to break-even. Great engineering wasn’t enough to save it from dwindling orders and a failed attempt by Jimmy Carter to sell production licensing Soviets. L1011 production ended prematurely in 1984. A victim of poor product differentiation and Rolls Royce.

Feature image by Allan Huse. Squadron 216’s last two Tristars taxi out on their final sortie at RAF Brize Norton.