Gripen Main Landing Gear Damaged During Unstabalised Short Field Landing

Gripen Main Landing Gear Damaged During Unstabalised Short Field Landing

On 13 June 2018 a a Swedish Air Force Saab JAS 39 Gripen attempted a short-runway landing at Piteå Airfield during a military exercise.  The approach was however unstabalised and the aircraft touched down hard and one main landing gear was damaged.  The pilot aborted the landing and returned to Luleå/Kallax.

Damaged Swedish Saab  JAS39C Gripen (Credit: Swedish Armed Forces via SHK)

Damaged Swedish Saab JAS39C Gripen (Credit: Swedish Armed Forces via SHK)

The Swedish Accident Investigation Board (the Statens Haverikommission [SHK]) say in their safety investigation report (published in Swedish) that:

The hard touch down was caused by a too steep approach angle, tailwind and low speed before setting.

jas39c approach

The damage…was due to an overload…caused by a too high rate of descend in relation to the aircraft mass in combination with a high nose-up attitude at touch down.

The damage components included a burst tyre, the right MLG side-stay locking mechanism, actuator and adjacent structure.

Damaged to MLG of Swedish Saab  JAS39C Gripen (Credit: Swedish Armed Forces via SHK)

Damaged to MLG of Swedish Saab JAS39C Gripen (Credit: Swedish Armed Forces via SHK)

Damaged Sidestay Lock Mechanism of Swedish Saab  JAS39C Gripen (Credit: via SHK)

Damaged Sidestay Lock Mechanism of Swedish Saab JAS39C Gripen (Credit: via SHK)

Investigators found that at a number of landings on the first day of the exercise were “very close to the runway edge”, by which they appear to mean the runway end.

Background

Bas 90 (Flygbassystem 90, Air Base System 90) was dispersed operating base concept used by the Swedish Air Force during the Cold War. Bas 90 was developed during the 1970s and 1980s from the earlier Bas 60 concept and involves runways and taxiways that coincided with local roads .

BAS90 airfield (Credit: Land Survey via SHK)

BAS90 airfield (Credit: Land Survey via SHK)

The concept influenced the Gripen’s design (along with maintenance simplicity to suit a conscript level of experience, working at these dispersed sites).  While the earlier Saab JA37 Viggen had reverse thrust for short field landings, the Gripen featured nose wheel braking and its effectiveness would be further enhanced by foreplane down force.

The Airfield

Piteå however was a civilian general aviation airfield and marked differently to a BAS90 site.  They SHK comment:

Piteå Airport [sic]…had not been used previously for short-runway landings. It does not have a military classification and differs in execution from the military classified runways previously practised against, among other things, in length and placement of the threshold markings.

Piteå Airfield (Credit  Piteå Flying Club via  SHK)

Piteå Airfield (Credit Piteå
Flying Club via SHK)

The threshold marking at Piteå Airport was located 39.5 metres from the runway edge, which differs significantly from the short-runways previously used [typically 200 metres at a BAS90 site].

A site reconnaissance had been conducted but “without an established method” and so “vital information was not communicated to the squadron’s pilots”.

SHK Conclusions

The incident was caused by the landing being completed despite the fact that the approach was not stabilized and that it ended with a too steep approach angle.

Contributing facts were the absence of clear criteria for abort landing in case the flight was not stabilized at a certain point during the approach.

SHK Safety Recommendations

The SHK recommended the Armed Forces:

  1. Introduce clear criteria for when a short-runway landing should normally be aborted. (RM 2019:01 R1)
  2. Develop and establish a method for producing decision-making documentation for the use of short-runways and runways that are not militarily classified, in order to ensure that conditions relevant to the security [safety] on such runways are discovered and that information about them is conveyed to the air operations. (RM 2019:01 R2)

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