Thanks to its unique thrust reverser the Saab 37 Viggen could land, come to a full stop, perform a Y-turn on the runway and take off in the opposite direction

Thanks to its unique thrust reverser the Saab 37 Viggen could land, come to a full stop, perform a Y-turn on the runway and take off in the opposite direction

By Dario Leone
Jun 18 2021
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To keep the Saab 37 Viggen landing distance short Saab developed a thrust-reverser integrated with the rear fuselage, still the only one if its kind on single-engined aircraft.

The Saab 37 Viggen featured an extremely advanced aerodynamic configuration for its time, combining a main delta wing with delta-shaped canard foreplanes. As told by Jan Jørgensen, Anders Nylén and Peter Liander in their book Saab 37 Viggen – The ultimate portfolio, this unconventional design enabled the Viggen to meet the Swedish Air Force requirement for speed of Mach 2+ at high altitude and ability to operate from 500 m runways.

The Viggen was powered by the Volvo Flygmotor RM8A/B afterburning turbofan. To keep the landing distance short Saab developed a thrust-reverser integrated with the rear fuselage, still the only one if its kind on single-engined aircraft.

‘Many jets have thrust reversers that turns part of the air stream from the engines forward to create a breaking effect after touchdown,’ explains pilot Thomas Kolb on Quora.

‘The Saab 37 Viggen fighter however had a thrust reverser that could actually be used to taxi backwards just like a car. Other aircraft had similar constructions, but not as intricate.’

‘With the Viggen, three triangular metal “petals” in the engine exhaust could be folded down by the pilot pulling out a T-shaped lever on the left side of the dashboard in the cockpit. This would then direct the entire air stream from the engine forward through slits around the back of the fuselage. If the reversor was activated in flight, the system would become armed so that the reversor plates would automatically close as soon as the main and the nose undercarriages became compressed when touching the ground. By pushing the throttle forward and adding power, the pilot could then get the aircraft to a surprisingly short stop. This was necessary due to the fact that the Viggen was designed to be able to operate from short makeshift runways, e.g. from car roads.

‘While backing up, the pilot however needed to be very careful not to use the wheel brake toe pedals, as the aircraft could easily tip over backwards for a tail strike.’

‘It was a popular maneuver with the Viggen during air shows to land in front of the audience, come to a full stop, perform a Y-turn on the runway and take off into the opposite direction.’

Kolb concludes;

‘In the picture below [taken by Milan Korbar and featured on PlanePictures.Net], the topmost of the three “petals” is folded down (it actually always dropped down by itself as the hydraulic pressure was released when parking).’

Photo credit: screenshot from YouTube video and Milan Korbar / Source: PlanePictures.Net

Thanks to its unique thrust reverser the Saab 37 Viggen could land, come to a full stop, perform a Y-turn on the runway and take off in the opposite direction

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Dario Leone

Dario Leone

Dario Leone is an aviation, defense and military writer. He is the Founder and Editor of “The Aviation Geek Club” one of the world’s most read military aviation blogs. His writing has appeared in The National Interest and other news media. He has reported from Europe and flown Super Puma and Cougar helicopters with the Swiss Air Force.

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