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How not to land a Boeing 737 in a strong crosswind

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How not to land a Boeing 737 in a strong crosswind

Old 28th Nov 2020, 09:00
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Join Date: Jun 2000
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How not to land a Boeing 737 in a strong crosswind

The accident report on Turkish Airlines Flight TK 467 a Boeing 737-800 that botched a crosswind landing at Odessa, Ukraine on 21 November 2019 has been published.
. There are many Boeing 737-800 aircraft operating in Australia and this scribe felt there would be professional interest among crews operating the type and could learn from this accident.
One unusual item contained in the report was the logged flying hours claimed by the captain as well as that of the first officer.
The captain claimed a total of 6094 hours. His time on type was 5608 of which the whole lot was claimed as in command. No dual and no copilot time on type It appears he had 496 total hours when starting on the 737 and thereafter logged everything as pilot in command.
The first officer had 252 hours total of which 175 hours was on the 737-800. On the face of it he would have flown only 77 flying hours total before joining the airline to eventually become second in command of the 737 at 252 hours or less.

As a former ATO I conducted numerous command instrument ratings or IPC's. The rules required inspection of the candidates log book before conducting the flight test. After the grant of a CPL it is rare for pilots to have their log books audited for accuracy and falsification of flying hours is not unknown. On several occasions there were blatant logging of false instrument flying hours. CASA told me they have no interest in the subject of instrument hours because the hours are impossible to audit unless they are accrued during dual training for an instrument rating. Recent aviation media reports indicated gross licence violations by certain overseas airline pilots and only a few weeks ago Vietnam Airlines terminated the contracts of several overseas pilots for falsifying their licences. Examiners in Australia need to be aware of their own responsibilities when it comes to checking of log book qualifications prior to tests. .
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Extracts from the Turkish Airlines incident report follows. No doubt eyebrows will be raised on reading the captains tortuous use of the nose-wheel steering tiller
A THY Turkish Airlines Boeing 737-800, registration TC-JGZ performing flight TK-467 from Istanbul (Turkey) to Odessa (Ukraine) with 136 passengers and 6 crew, was on final approach to Odessa's runway 16 when the crew initiated a go around at very low height. The aircraft climbed to 8000 feet, positioned for another approach to runway 16 and landed about 25 minutes later at 20:54L (18:54Z). The aircraft came to a stop on the left edge of the runway with the nose gear collapsed and the nose beyond the edge of the paved surface. The aircraft was evacuated via slides. No injuries are being reported. Mode-S Transponder data transmitted by the aircraft suggest the aircraft actually touched down on first approach and performed a balked landing. The airline reported the aircraft departed the runway after landing in Odessa, the passengers and crew were evacuated without any injuries.

On Nov 22nd 2019 Ukraine's NBAAI reported that after landing on runway 16 the Boeing 737-800 registration TC-JGZ rolled out of the runway. When attempting to return onto the runway the nose gear collapsed and the aircraft stopped at the left edge of the runway with the right main gear remaining on the runway surface and the left main gear outside of the runway. The occurrence was rated a serious incident and is being investigated.

On Dec 19th 2019 the NBAAI reported in their monthly bulletin, the flight crew indicated the reason for the go around from about 150 feet AGL had been an unstabilized approach. After entering a hold to wait for improved weather conditions the crew performed a second approach. After touchdown the aircraft began to drift to the left, rolled out of the runway with all gear and went over soft ground for about 550 meters until the right main gear and the nose of the aircraft returned onto the paved surface. The aircraft came to a stop 1612 meters past the runway threshold. The aircraft sustained substantial damage to the belly of the fuselage and the left engine. The NBAAI is investigating, the Turkish AIB have joined the investigation.

On Nov 19th 2020 Ukraine's NBAAI released their final report. : The cause of the accident, i.e. runway excursion, which caused significant damage to the structural elements of the aircraft B-737-800 TC-JGZ of Turkish Airlines, which took place on 21.11.2019 during landing at «Odesa» Aerodrome, was failure to maintain the direction of the aircraft movement during the landing run in the conditions of a strong crosswind of variable directions.

Contributing Factors:
- Use by the crew of the landing approach method using the Touchdown in Crab technique, which is not recommended by FCTM B-737NG document for use on dry runways in the conditions of a strong crosswind;- Untimely and insufficient actions of the crew to maintain the landing run direction;- Presence of a significant cross component of the wind; - Effect of an omnidirectional wind – from cross-headwind to cross-tailwind directions – during the landing run.

The captain (42, ATPL, 6,094 hours total, 5,608 hours on type, 5,608 thereof as commander) was pilot flying, the first officer (31, CPL, 252 hours total, 175 hours on type) was pilot monitoring.
According to the CVR, during the flight in the FIR control area of Romania (call sign - "Constantsa"), prior to descent, at 17:55, the crew listened to the ATIS "November" information for 17:34 of the «Odesa» Aerodrome and began approach briefing.

Note: ATIS for 17:34 contained the following information about the wind direction and speed: touchdown zone – 070º, 9 m/s, gusts maximum 13 m/s, minimum 05 m/s, varies in the sector from 030º to 090º; runway end: 080º, 12 m/s, gusts maximum 16 m/s, minimum 06 m/s, varies in the sector from 040º to 100º. The values of the cross wind component were 13 m/s (25 knots) and were less than the maximum allowable ones for taking decision to perform landing.

Taking into account the wind direction change (from 30º to 90º) and wind gusts up to 13 m/s, the tail wind component reached 7.8 m/s, which was equal to 15.6 knots and exceeded the limits (15 knots) set by Boeing 737-800 Flight Manual. During the approach briefing, the crew did not discuss the non-conformity of the force of the tail wind, and the PIC took decision to continue the landing approach.

During the approach briefing, PIC instructed the co-pilot to monitor the value of the cross wind component with FMC ("progress page"), drew his attention to adverse weather conditions, in particular, that the wind force values are close to the maximum allowable ones, and urged the co-pilot to be careful because of the possibility of go-around ("Weather is a threat for us we have to be careful because maybe 90 percent we gonna do a go-around, ok?"). At the same time, the PIC did not draw attention of the co-pilot to the fact that, taking into account a significant change in wind direction, the tail wind component reached 7.8 m/s (15.6 knots) and exceeded the established limits.

The AUTOBRAKE automatic braking system was initially set to position "3", however, according to the PIC’s instructions, the co-pilot should have been ready to set it to position "MAX", if necessary.

At 18:04:24, the crew started the descent down to FL 300. During the descent, the crew listened to ATIS "Quebec" for 18:05, which contained the information about the following values of wind direction and speed: touchdown zone - 080º, 9 m/s, gusts – maximum 15 m/s, minimum 06 m/s; runway end - 090º, 10 m/s, gusts - maximum 15 m/s, minimum 06 m/s, wind direction changed from 050º to 120º.

The meteorological minimum qualification of the crew allowed landing at the values of cloud ceiling and visibility indicated in the ATIS. The approach was performed according to the approach route OGLAR 3Y and vectoring till capture of Runway 16 ILS. The descent to the altitude of 2,000 feet was within normal limits. At 18:22:29, the ATC controller of the CTA Odesa OVT sector gave clearance to the crew to descend to the absolute altitude of 2,000 feet and gave clearance to the ILS landing approach to Runway 16 and instruction to report the localizer beam capture, which was confirmed by the crew. At 18:26:09, the ATC controller of the CTA Odesa OVT sector asked the aircraft crew about the localizer beam capture. The aircraft crew confirmed the localizer beam capture.

The ATC controller of the CTA Odesa OVT sector informed the aircraft crew about its location relative to the touchdown point and instructed to switch the communication to ATC controller of Odesa TWR on the frequency of 125.5 MHz, which was confirmed by the crew. The NBAAI subsequently analysed the aircraft configured for the ILS approach, captured LOC and GLD and was on final approach when the crew initiated a go around reporting unstable aircraft attitude (according to FDR the speed was 171 KIAS, 18 knots above Vapp). The aircraft entered a hold waiting for better winds. At 18:51:23, the controller provides the crew with the updated information about the wind 080º, 11 m/s, maximum 15 m/s. During transmission of the updated information, the controller no longer draws the crew’s attention to significant changes in the wind direction. At 18:52:32, the Tower controller informed the crew about the wind: 080º, 12 m/s, maximum 15 m/s and gave clearance to land on the Runway 16.

Note: in the process of landing approach and on final, the co-pilot shall monitor and constantly inform the PIC about the cross component of the wind, which at this time, at the flight level, ranged from 23 to 28 knots.

At 18:53:18, the crew started to perform the Landing Check List, during which the landing gear extension, spoiler arming and flap deployment to 30° were checked. At 18:53:56, after the "One thousand" sound signal, the PIC and co-pilot said that the plane was stabilized. Note: according to the FDR data, the aircraft was indeed stabilized by all parameters. At 18:53:59, the controller provided the crew with the information about the wind: 090º, 11 m/s, maximum 13 m/s.

At 18:54:56, after the Minimums sound signal, the PIC announced his decision to continue the landing approach. From 18:55:10 to 18:55:14, the aircraft synthetic voice was calling out the altitude ("Fifty, forty, thirty, twenty, ten".) At 18:55:15, the plane reduces the pitch from + 3.5º to + 2.6º.

At 18:55:16, the touchdown took place first by the right landing gear at a distance of 444 m from the threshold of the Runway 16 and to the left of the centerline at the distance of 0.4 m with heading 051º and right roll of 3º (according to FDR data.) PIC deflects the right pedal to the angle of 5.6º (out of possible 12º.) The magnetic heading increased by 2º and reached 153º, the aircraft pitch decreased from + 2.6º to -0.7º, which caused the left landing gear touchdown at the distance of 454 m of the threshold and 6 m to the left of the centerline of the Runway 16, and nose landing gear touchdown at the distance of 552 m from the end and 1.5 m to the left of the centerline of the Runway 16. At 18:55:17, the co-pilot confirmed that the spoilers were deployed automatically ("Speed brake up".)

At 18:55:18, the PIC switched the reverse thrust to position "2" and again, for 2 seconds, displaced the right pedal to 4.6° (out of possible 12º), but it had no effect because the aircraft heading remained 153º. The co-pilot did not report that the reverse thrust was unlocked ("REVERSE UNLOCK"), the automatic braking system started operation ("AUTOBRAKE IN USE"), the reverse thrust was switched to position "2" ("REVERSE NORMAL"), as required by the crew operation technology. In addition, when the aircraft deviated from the centerline of the Runway 16 during the landing run, the co-pilot should have warned the PIC ("DRIFTING TO THE LEFT".) At 18:55:21, the PIC, at the speed of 130 knots, turns the wheels of the front landing gear to the right through large turn angles up to 78º.

As a result, the wheels of the front landing gear began to skid on the runway, as evidenced by a clear solid black mark from the wheels of the nose landing gear on the runway, which also indicates that the PIC turned the wheels of the nose landing gear through large turn angles. At this speed, the aircraft weighing 63,000 kg at the distance of 848.76 m from the runway threshold and 13.53 m to the left of the centerline of the Runway 16 with MH 153º at landing heading 157° continued to drift to the left. At that, the tires of NLG wheels begin to crumble to pieces. However, the FCOM warns against using large wheel turn angles (78º) until the landing run speed is reduced to the steering speed.

At 18:55:25, with MH 151º at a speed of 111 knots with the pedals deflected to the right by 7º (out of maximum 12º), the rudder was deflected to 18.7º (out of the maximum 30º), NLG entered the soil. At this point, the flight recorders recorded almost the maximum deflection of the right pedal, which lasted until 18:55:43 (speed was 27 knots, distance was 1638 m from the entrance threshold.) At 18:55:44, the deflection of the right pedal decreased to 8º, and then to 0º.

Subsequently, after collapse of the nose landing gear, for 23 seconds, the ground speed began to decrease from 107 to 2 knots. At 18:55:27, the pitch of the aircraft was -5.6º; right roll +20º, MH 152º, maximum pedal deviation to the right 11.2º (out of the maximum 12º), rudder 27° (out of the maximum 30º) and speed 101 knots, which evidenced NLG collapse in the direction opposite to the movement. At 18:55:28, the plane completely rolled out of the runway onto the soil and moved with MH 158º-159º for 3 seconds. At 18:55:31, the aircraft increased its heading to 165º at a distance of 1360 m from the entrance runway threshold. Over the next 8 seconds, the aircraft increased its heading up to 171º.

From 18:55:39 to 18:55:50, the aircraft heading decreased from 170º to 159º. The aircraft came to rest at 18:55:51 at a distance of 1683 m from the entrance threshold of the Runway 16 and at 27 m from the runway centerline to the left.

Section 6 (p. 6.45) of the FCTM B-737NG provides three techniques for landing in strong crosswinds on a dry runway. The values of the flight parameters during landing, such as roll, magnetic heading and rudder deflection, indicate that the crew performed the landing and landing approach using the Touchdown in crab technique (landing with an angle of allowance till touchdown), which is not recommended by FCTM B-737NG document for dry runways with strong crosswinds. At the time of touchdown of the main landing gears, it is very important to maintain with the rudder the aircraft longitudinal axis parallel to the runway centerline until the front landing gear is lowered, simultaneously deflecting the ailerons against the wind. However, the crew did not do so and lowered the NLG at the heading 151º at MHland = 157º, which caused a gradual deviation of the aircraft from the runway centerline to the left.

After NLG lowering, it was difficult to the crew to turn the aircraft to the heading 157º, having a turn angle from the nose landing gear just only 7º. A significant landing weight of the aircraft (63,000 kg) and its landing speed during the landing run caused emergence of forces that contributed to the aircraft veering off. These forces, together with the cross wind force component, reverse thrust force component, as well as an insufficient rudder deflection angle, prevented the aircraft from returning to the runway centerline or, at least, to a position parallel to the runway centerline. In his Statement, the PIC notes that, having realized ineffectiveness of the rudder deflection, he took decision to apply "Nose wheel steering" to large angles up to 78º, although FCTM does not recommend using this mode at speeds higher than the steering speed.

Despite the fact that the nose landing gear was hydraulically rotated through a significant angle (almost perpendicular to the aircraft movement), this did not allow the aircraft reaching the centerline or position parallel to it. The turned wheel of the nose landing gear began to skid, as seen in the photo, when two black stripes from the tires of the nose landing gear merge into one continuous stripe.

.

Last edited by Centaurus; 28th Nov 2020 at 09:20.
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Old 28th Nov 2020, 23:03
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Sometimes the received wisdom that autobrakes should be used to taxi speed is demonstrated to be sub-optimal. Perhaps if the PIC had ever flown a DC-3, or operated a wheelchair, he would have understood the power of differential braking for directional control. But what do I know? Landing in a gusty 30 kt crosswind, while vexing, should not tax the abilities of an average pilot. Perhaps there was something else going on with the aircraft?
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Old 29th Nov 2020, 00:21
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I guess god wasn’t willing on this occasion and the captain was found wanting.
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Old 29th Nov 2020, 00:27
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Originally Posted by Australopithecus View Post
Sometimes the received wisdom that autobrakes should be used to taxi speed is demonstrated to be sub-optimal. Perhaps if the PIC had ever flown a DC-3, or operated a wheelchair, he would have understood the power of differential braking for directional control. But what do I know? Landing in a gusty 30 kt crosswind, while vexing, should not tax the abilities of an average pilot. Perhaps there was something else going on with the aircraft?
I suggest you read the report again......and note one thing especially......Rudder and aileron usage, or lack there of....
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Old 29th Nov 2020, 02:26
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Originally Posted by ACMS View Post
I suggest you read the report again......and note one thing especially......Rudder and aileron usage, or lack there of....
Well, yeah, he lands crabbed contrary to the guidance in the publications. And he only uses about half of the available rudder authority after touchdown, and then decides 78° of nosewheel deflection might work. None of those actions are what you'd expect from someone with a stitch of sympathy for the aeroplane. My point was that even after all that, differential braking may have prevented the excursion.
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Old 1st Dec 2020, 19:39
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“Boomps a daisy. It’s enough to make you weep.”
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