Safety Matters and Safety Briefs are based on the AAIB Bulletin and UK Airprox Board reports, with additional material from the US National Transportation Safety Board
Mustang midair, undercarriage overlooked and other safety news
Aircraft Type: (Both) NA P-51D Mustangs G-SHWN and G-BIXL Date & Time: 23 September 2017 at 1530 Commanders’ Flying Experience: 1 ATPL, 18,000 hours, 600 on type 2 ATPL, 19,000 hours, 87 on type Last 90 days: 1 9 hours 2 119 hours Last 28 days: 1 5 hours 2 37 hours
The two aircraft were part of a formation flypast at a Duxford airshow that included a B-17 Fortress that had already completed a flypast with a Douglas DC-3 and C-47. For the next sequence the Mustangs were to join the Fortress for another flypast, then separate from the bomber and give a display of formation aerobatics. G-SHWN was to lead, with G-BIXL following.
The P-51D pilots had arrived at Duxford the day before the airshow and that evening discussed the formation aerobatics they planned to fly. It was the same sequence they had flown together at another show three weeks earlier, when the pilot of G-SHWN had led the display, as he was to do on this occasion. Next morning they both attended the main pilots’ airshow briefing at Duxford, after which the pilots of the C-47, B-17 and P-51DS were given an additional formation briefing by the DC-3’S pilot, who was to be the leader of their part of the display. In addition to the verbal briefing, he gave the pilots a written briefing.
When discussing how the P-51DS would join the B-17, the lead Mustang’s pilot stated that, after taking off separately from the other aircraft, they would initially practice some formation aerobatics away from the airfield, with the second P-51D on the right. After the DC-3 and C-47 had completed their flypast with the B-17, the Mustangs would join the B-17, G-SHWN would join on its right with G-BIXL on its left. The Mustang pilots then discussed what they would do during the formation aerobatics. At this time, G-BIXL’S pilot’s focus was on this part of the display, as he regarded the formation flypast as “bread and butter flying”, having flown many of these before, in and with various types of aircraft.
About thirty minutes before takeoff, the Mustang pilots met at their aircraft and discussed the display again. The focus was again on the formation aerobatics, which they walked through together. While the pilot of G-BIXL waited in the cockpit to start, he went through the formation sequences in his head with his eyes closed, but did not go through the join with the B-17. After takeoff, and having completed the practice aerobatics with G-BIXL on his right, the pilot of G-SHWN became visual with the B-17, which was flying at about 500ft agl, so the Mustangs flew towards it to commence the join.
B-17 started a right turn back towards the airfield, and the P-51s passed below and through its 6 o’clock in a left turn, before reversing the turn. Once in the right turn, G-BIXL’S pilot flew through the B-17’s 6 o’clock to join on its right. As he did, he looked at G-SHWN, from which he was moving away, and believed it was going to join on the B-17’s left. Thinking that both P-51s were now on their nominated sides of the B-17, he looked inside the cockpit to check his instruments. At this point he believed that the airspace to the B-17’s right was only for his aircraft and he was thus clear to fly into position for the flypast. He briefly looked in his nine o’clock and saw nothing, but was not concerned that he could not see G-SHWN, as they were both at low level and it may not have been easily visible against the ground due to its camouflaged paint scheme. He also believed the pilot would have been doing the same as him, flying low and fast before climbing into position with the B-17.
G-BIXL’S pilot’s next recollection was that the aircraft nosed down slightly and started to shake moderately. He checked the engine instruments, which were indicating normally, and believed something had detached from his aircraft. As the shaking increased, he turned towards Duxford, transmitted a Mayday and made an uneventful landing on grass Rwy 06L.
The pilot of G-SHWN said that as the B-17 was in its right turn, the P-51s passed through its six o’clock in a left turn and below, before reversing the turn. Just before the right turn reversal he looked over his right shoulder and saw G-BIXL, but this did not concern him as they had briefed to do a loose formation join. G-BIXL next appeared descending from above right, and its tailplane passed through his propeller arc as he was about to move up and into position on the B-17. He did not see G-BIXL prior to this, as he was predominately concentrating on the B-17 that was then in his eleven o’clock. He felt a very slight knock which made him realise they had collided. Having heard G-BIXL’S pilot’s Mayday, he followed the B-17, and once the other Mustang had landed safely, separated from the Fortress and landed on hard Rwy 24.
Examination confirmed that damage on both aircraft had come from contact between the propeller blades of G-SHWN and the left horizontal stabiliser of G-BIXL. The propeller strike had been within a few centimetres of the control cables for the elevator trim system, but resulted in structural damage only. G-SHWN’S four propeller blades all exhibited scuffing to the paint, but no visible structural damage.
G-BIXL’S pilot later stated that when he draws a diagram of a formation display he usually annotates an aircraft symbol with ‘ME’ to indicate which aircraft is his in the formation. On this occasion he annotated ‘P-51’ against both symbols representing the Mustangs, and was “fairly sure” that had he differentiated between the two symbols he would not have joined the B-17 on the right. He would
ensure that he always does so in future.
Also, he said, that had all the pilots walked through the display on the ground, as is generally the norm, and had he flown the whole display through in his mind during his preflight preparation, he was almost certain his misunderstanding would have been noticed and corrected before takeoff. The two Mustang pilots had only walked through the formation aerobatics as the join and flypast with the B-17 was considered a “standard piece of flying” that they had flown recently, albeit with a different lead aircraft. He believed he was likely to have suffered from ‘risky shift’ as a result of having done similar joins “hundreds of times”. (‘ Risky shift’ is a tendency for individuals to make more daring decisions when they are in groups, than when they are alone – Ed.) He stated that in future he would keep the lead aircraft visual until it was established in formation with the flypast’s lead aircraft before moving to his briefed side. Had he believed G-SHWN was on the incorrect side he would have sought clarity over the R/T.
The AAIB report concludes: ‘The P-51 pilots had flown many formation flypasts together before, in different types of aircraft. They had also practised the formation aerobatics part of the display three weeks prior to the accident. The pilot of G-BIXL agreed and acknowledged at the briefing that [he] would formate on the left side of the B-17. However, having planned and practised the formation aerobatics in echelon right he may have had some confirmation bias to support his belief that being on the right of the B-17 for the flypast was correct.
‘The two P-51s collided due to a combination of human factors. The pilot of G-BIXL did not annotate his diagram of the display sequence to show which was his aircraft. This removed one of the possible means of confirming which side he had been briefed to join the B-17. There appear to have been omissions, possibly resulting from a degree of complacency, during the briefings and subsequent walk through, where the join and flypast with the B-17 were not considered. Best practice would have been for the pilot of G-BIXL to have remained visual with G-SHWN until it was in the final formation position. It was only providence that prevented this accident from resulting in a catastrophic outcome.’
As a result of this accident the CAA has made the following addition to Appendix C of Edition 15 of CAP 403 Flying Displays and Special Events: Safety and Administrative Requirements and Guidance that was published in March 2018: ‘Useful guidance for display pilots – Briefings and walk throughs. It is essential that in addition to the Flying Display Director’s written and verbal briefings that all display items consisting of formations are thoroughly briefed. It is vital that every member of the formation has a clear picture of the objectives of the formation as a whole and of their individual positioning and responsibilities within it. Walk throughs are an integral part of this briefing process and it is strongly recommended that they are adopted as a standard part of all formation briefings [AAIB’S emphasis]. Walk throughs are not exclusive to formation briefs and can also be of benefit to the solo display pilot.’
Aircraft Type: Diamond DA 42M Twin Star Date & Time: 6 April 2018 at 0743 Commander’s Flying Experience: CPL, 9,000 hours, 4,000 on type Last 90 days: 100 hours Last 28 days: 27 hours As part of a dual flight in preparation for a multiengine class rating test the student pilot rejoined the Bournemouth circuit and made an approach with flaps configured normally. He had difficulty maintaining the runway centreline and correct
speed, due to what he described as “challenging” conditions in turbulence and an estimated 14kt crosswind, but a satisfactory touch-and-go landing was made and the aircraft repositioned downwind for flapless landing.
While downwind, the student completed the prelanding checklist, which includes confirmation that the parking brake is selected ‘Off’. He then commenced the ‘Final Descent’ checklist and believes he said “gear down” before reducing power and starting to turn onto base leg. However, the instructor recalled that the student placed one hand on the undercarriage control lever and was about to turn onto the base leg, when it became apparent that neither of them could see a preceding aircraft. Because of this the instructor asked the student to continue downwind but, after a short time, they spotted the aircraft ahead and as they turned onto base leg, the instructor noticed that the parking brake was on and pointed this out, but the student said that he thought the parking brake lever was off. They then discussed the fact that the aft positions of the two adjacent heating controls are labelled ‘Off’, whereas the parking brake lever functions in the opposite sense – its aft position is labelled ‘Lock’ and the checklists refer to this as ‘On’. Consequently, the student released the parking brake, but the instructor remained distracted for several seconds, contemplating why the parking brake lever had been erroneously set.
The aircraft was established on short final, but offset from the centreline, before the instructor switched his attention away from the issue of the lever positions. He considered instigating a go-around but decided to coach the student back towards the centreline. While he did this, the student made large power changes, trying to control the airspeed, which was increasing. Fully occupied monitoring the student’s actions, the instructor overlooked a required check that the aircraft was stable and in a landing configuration at 100ft aal. As they passed over the runway threshold the student gradually reduced power and the aircraft made a gentle touchdown on the runway, and it then became apparent that the undercarriage was up and that the propellers were striking the surface as the aircraft slid to a halt. It had suffered damage to its propellers, engine gearboxes, lower engine cowlings and underside panels.
Following the accident, the instructor stated that both he and the student overlooked checking the undercarriage indications for three reasons: they were distracted by looking for the traffic ahead in the circuit, there was some confusion due to the mis-selection of the parking brake, and they continued an unstable approach. The student reflected that he might have been distracted, either by the other traffic or by the parking brake position, and that it is possible he did not move the undercarriage lever. Earlier in the flight, and on previous flights, he had been asked to respond to simulated emergencies using ‘touch drills’ only – touching the relevant levers or switches but not activating them – and it was possible, because of his high workload, that he inadvertently touched the landing gear lever but did not move it.
The aircraft operator stipulates an ‘Approach Gate’ at 400ft aal when on a visual approach and, at this point, the student should have called “400 stable” or “400 not stable, go-around”. One of the parameters which has to be checked before calling “400 stable” is that the undercarriage is down, with three green indicators lit. Neither crewmember recalled this being said and the student suspected that he either forgot it, because he was working hard to manage the approach, or that he made it without actually looking at the position of the undercarriage lever.
The aircraft operator’s initial report suggested that the parking brake may have been selected ‘On’ instead of the undercarriage lever being set to ‘Down’. When this was noticed, it led to distraction and some confusion, partly due to the different directions in which the parking brake lever and the adjacent heating controls operate. This distraction prevented the instructor from effectively monitoring the student, who was working at high capacity during the approach. The operator plans to review the operating parameters and the adequacy of the aural warning system, and to consider incorporating the labelled positions for the parking brake lever in the aircraft checklists. It also recommends that crews be reminded of the necessity for carrying out entire checklists correctly and without interruption, of the prime importance of monitoring students’ actions, especially at crucial stages of flight and that a go-around is often the best and safest course of action if an approach becomes unstable or is rushed.
Helicopter Safety Seminar
The CAA and British Helicopter Association are holding a Helicopter Safety Seminar at Aviation House, Gatwick Airport on 6 September. It will run from 1000-1600, with a light lunch provided. The seminar will include a briefing on the Safety Review of Onshore CAT (including emergency services), NCC and SPO operations which the CAA has implemented. ‘Applications to attend are welcome from all work areas of the operations listed and early booking is advised as we anticipate that this will be a well subscribed event,’ advises the Authority. Applications should be made to: ali[email protected]
Low-res image of the DA42M after its wheels-up landing. The aircraft operator plans to review operating procedures and checklists