A hard landing occurs when an aircraft or spacecraft hits the ground with a greater vertical speed and force than in a normal landing. The terms hard landing and firm landing are often confused though are inherently different. A hard landing is never intended and if an aircraft has had a hard landing, it must be inspected for damage before its next flight.[1] In contrast, depending on aircraft type (e.g. Boeing 737) and/or environmental conditions (e.g. gusty or crosswind conditions, wet runway, etc.) a firm landing is intended and even demanded by the aircraft manual.
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Landing is the final phase in flight, in which the aircraft returns to the ground. The average vertical speed in a landing is around 2 metres per second (6.6 ft/s); any greater vertical speed should be classed by crew as hard. Crew judgment is most reliable to determine hard landing, as determination based on recorded acceleration value is difficult and not advisable,[1] partially because there is no recording of true vertical acceleration.[2]
Hard landings can be caused by weather conditions, mechanical problems, overweight aircraft, pilot decision and/or pilot error. The term hard landing usually implies that the pilot still has total or partial control over the aircraft and is aware of the terrain proximity, as opposed to a uncontrolled descent into terrain or a controlled flight into terrain (both of which can be called a crash). Hard landings can vary in their consequences, from mild passenger discomfort to vehicle damage, structural failure, injuries, and/or loss of life.
Hard landings can cause extensive damage to aircraft. For example, on 20 June 2012, a Boeing 767 of All Nippon Airways landed with such force that a large crease formed in the aircraft's skin.[3]
When the final approach isn't stabilised, the crew is to abort and go around; this was the recommendation of the Australian Transport Safety Bureau after investigating the hard landing of a Malaysia Airlines Airbus A330 at Melbourne Airport after arriving from Kuala Lumpur on 14 March 2015.[4][5]
For helicopters, a hard landing can occur after mechanical or engine damage or failure when the rotor(s) are still intact and free to turn. Autorotation, in which airflow over the rotors keeps them turning and provides some lift, can allow limited pilot control during descent. As an unpowered descent, it requires considerable pilot skill and experience to safely execute.
A hard landing of a spacecraft such as a rocket stage usually ends with its destruction and can be intentional or unintentional. When a high-velocity impact is planned (when its purpose is to study consequences of impact), the spacecraft is called an impactor. This is sometimes humorously referred to as lithobraking.
See also
editReferences
edit- ^ a b Garber, Ralph Michael; Van Kirk, Lawrence, "Conditional Inspection", Aero, no. 14, Boeing, archived from the original on 2021-03-01, retrieved 2021-10-01
- ^ Guillaume Aigoin, Characterising hard landings Archived 2017-03-15 at the Wayback Machine / EASA EOFDM Conference, 12 January 2012, page 7: "The vertical parameter is neither vertical nor an acceleration … It is the normal load factor in the aircraft reference frame is not sufficient for assessing contact severity!"
- ^ "ASN Aircraft accident Boeing 767-381ER JA610A Tokyo-Narita Airport (NRT)". Aviation-Safety.net. Archived from the original on 17 November 2018. Retrieved 17 November 2018.
- ^ Richard N. Aarons (Jun 22, 2017). "Unstabilized Approach?". Aviation Week Network. ATSB: When In Doubt, Go Around. Archived from the original on December 20, 2019. Retrieved October 1, 2021.
- ^ "Hard landing involving an Airbus A330, 9M-MTA, Melbourne Airport, Victoria on 14 March 2015", Aviation safety investigations & reports, ATSB, 5 April 2017, archived from the original on 7 May 2021, retrieved 1 October 2021
External links
edit- Stabilized Approach and Flare Are Keys to Avoiding Hard Landings / Flight Safety Foundation, FSF Digest, August 2004