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| Name | Landing Accident-Rarely Seen Porpoising [For details click on down arrowhead to the right.] |
| Video Uploader | Video From EntertainMeThai |
| Upload Date | This Video Uploaded At 22-12-2011 21:41:59 |
| Video Discription | This video shows a landing accident of a type that is rarely caught by the camera. The "Porpoising" landing takes place at Rtishchevo, a town in south-western Russia, about 300miles/500km SE of Moscow. It involves a LET L-410 Turbolet, an a/c manufactured in the Czech Republic. The a/c sustained sufficient damage during the landing to cause it to be written off. There are some valuable flying lessons to be learnt from this accident, so it's worth analysing the sequence of events. On the first touchdown, the L-410 is flying approximately level & parallel to the runway, so both the nosewheel & main gear contact the runway at virtually the same time. The touchdown is not at all heavy, but because the a/c has been approaching with excessive airspeed & appears to not be reducing that speed, it is assumed the PF (Pilot Flying) has had too much power selected on finals & during the initial flare. In addition, it appears the PF has failed to pull the power back to idle on touchdown. The combination of an airspeed which is still sufficient to keep the a/c flying approximately level with a level-fuselage attitude(ie an airspeed which is still somewhat above stall speed or maybe even above approach speed), of too much power (ie power not back at idle) & of the rebound from the undercarriage oleo springs that have been compressed on touchdown, has resulted in the a/c bouncing back into the air. The PF now pushes the nose down to get the a/c heading back towards the runway, but in doing so, he has forced the a/c to adopt an attitude where the nosewheel is now closer to the runway than the main gear, so the nosewheel strikes the runway first. This forces the rest of the a/c to rotate rapidly around the nosewheel which slams the main gear onto the runway. This causes the a/c to pitch its nose up & to bounce back into the air. This nosewheel-main-gear-strike sequence is repeated four more times with increasing severity of each subsequent pitch-up & bounce (called "Porpoising"). Eventually, on the last nosewheel strike, the nosegear collapses & the a/c screeches to a halt. From this analysis, the following general rules can be confirmed: (1) An airspeed on finals that exceeds the standard approach speed, does have advantages & may even be mandatory in times of turbulence, windsheer etc, but it can also have some distinct disadvantages as seen in this accident. This disadvantage is in addition to the commonly assumed one of insufficient runway stopping distance. (2) If the approach speed has been deliberately maintained above normal on finals, take positive steps when safe to do so, to reduce the airspeed on late finals, &/or to reduce the power either immediately before the flare, or as soon as the flare is initiated. (3) On touchdown, immediately & positively reduce the power to idle. (4) Do not deliberately allow the nosewheel to contact the runway before the main gear during a landing. (5) If the nosewheel is inadvertently allowed to contact the runway first & a bounce results, immediately apply power & initiate a go-around. (6) In the rare event that a go-around is not possible (eg a one-way strip), act as follows (6a) Immediately select an attitude which will allow the main gear to touch down before the nosewheel. This attitude will be somewhere between the level-fuselage attitude & the flare attitude. The level-fuselage attitude will be seen from the cockpit when the a/c is static on flat ground, ie when both the nosewheel & main gear are on the ground/runway. This is an important attitude, so make sure you commit it to memory & reconfirm it whenever you can either before start, or while taxying, or immediately before takeoff. (6b) While selecting the attitude, maintain power above idle or if necessary, immediately apply a little power to prevent the a/c from stalling. (6c) As soon as the required attitude has been selected, reduce thrust to idle. If the a/c is well above the runway, reduce thrust slowly to allow the a/c to sink to touchdown on the runway without stalling. If the a/c is already close to the runway, reduce thrust positively as with a normal flare, to allow the a/c to touchdown. Flare as necessary to make a smooth touchdown. (6d) Note that the above sequence can consume both time & runway before touching down. The possibilty of not stopping before the end of the runway is greatly increased. A go-around is almost always the best option, so remember to use the above technique only if there is absolutely no option for a go-around. (7) Note also that the above sequence consists only of general rules. They are not intended to apply specifically to the L-410 or to any other specific a/c type. PFs should modify these rules as necessary, to suit their particular a/c. Thanks for visiting & for any comments, & keep your flying safe, & your instructing diligent. |
| Category | Travel & Events |
| Tags | Accident | Landing | Crash | Plane | aircraft | a/c | airplane | aeroplane | LET | L-410 | L410 | Turbolet | Rtishchevo | Russia | Airport | bounce | bouncing | Porpoising | Porpoise | nosewheel-first-landing | heavy-landing | flying-safety | landing-technique | flare | touchdown | high-approach-speed | flying-training | flying-instruction | accident-analysis | inadequate-training | inappropriate-training | avoiding-flying-accidents | flying | undercarriage-collapse | gear-collapse | nosewheel-collapse | Авария | в | Ртищево | Авария-в-Ртищево |
