AN26, vicinity Birmingham UK, 2020
AN26, vicinity Birmingham UK, 2020
On 16 July 2020, an Antonov AN26 on which a new Captain’s final line check was being performed made two consecutive non-precision approaches to Runway 33 at Birmingham both of which resulted in ATC instructing the aircraft to go around because of failure to follow the prescribed vertical profile. A third approach using the ILS procedure for runway 15 was successful. On the limited evidence available, the Investigation was unable to explain the inability to safely perform the attempted two non precision approaches to runway 33 or the continuation of them until instructed to go around by ATC.
On 16 July 2020, an Antonov AN26B (UR-CQD) being operated by Vulkan Air on a non scheduled international cargo flight from an unrecorded airport to Birmingham which was being used for a final line check made two consecutive non-precision approaches to runway 33 at night and in VMC for the final stages of both approaches, neither of which were flown in accordance with the corresponding procedure. Both were discontinued on ATC instructions before a third ILS approach to runway 15 was then completed normally.
A Serious Incident Investigation was carried out by the UK AAIB based on information provided by the flight crew involved, the aircraft operator and ATC. It was noted that the 44 year-old trainee Captain occupying the left hand seat had a total of 2,512 hours flying experience which included 624 hours on type and was undergoing a Final Line Check to qualify as a Captain on type. Corresponding experience details in respect of the supervising Training Captain, who was also a “senior manager” at the operator, were not recorded.
It was established that, with the trainee Captain acting as PF, the aircraft was cleared to descend to 2,000 feet QNH and when 12 nm from touchdown was established on the LOC with clearance to descend further with the procedure (the UK AIP version of which is depicted in the illustration below).
Descent from the 2000 feet platform altitude begins at 5.1 nm from touchdown but with half a mile to go, the aircraft was still descending through 2,500 feet. This descent continued until the aircraft reached approximately 2000 feet where it levelled off. When the aircraft was 3 nm from touchdown, it was still maintaining 2,000 feet which put it 660 feet above the correct vertical profile. ATC reminded the crew of this and the need to begin a descent but then, “a few seconds later” the same controller instructed the flight to commence the standard missed approach for the procedure by climbing straight ahead to 3,000 feet. Initially, the aircraft was observed to make a left turn but then returned to the runway heading and was re-cleared to climb to 4,000 feet and provided with radar vectors for a further LOC/DME approach to Runway 33.
The aircraft was subsequently established again on the runway 33 LOC at 10 nm and ATC reminded the crew that there was no GS available. The aircraft was cleared to descend with the procedure but then began descent from the 2000 feet platform altitude at 8 nm from touchdown, almost 3nm too early. With 7 nm to go, the aircraft was descending through 1,600 feet and thereby 400 feet below the correct procedure altitude. The controller did pass altitude and range information to the flight but did not warn the crew that they were significantly below the correct altitude. The aircraft continued its descent and after a further mile was passing 1,500 feet, 500 feet below the correct altitude and at this point, the controller “gave the pilots a terrain warning and instructed them to go around”.
Editor's Note: Although not mentioned in the Official Report, the METARs for around the time of the two unsuccessful approaches gave the lowest cloud as BKN (broken) with a base at 1100/1200 feet aal which would have been approximately equivalent to 1400-1500 feet QNH. It is therefore possible that visual contact with the intended landing runway may not have been available until around that altitude.
The UK AIP LOC/DME approach procedure chart for runway 33 at Birmingham. [Reproduced from the Official Report]
In the absence of any response and continued descent, the go around instruction was repeated as the aircraft passed 1,400 feet, 600 ft below the correct altitude. This time, the crew responded that they had the runway in sight and were “approaching the glideslope” to which the controller again reminded them that there was no glideslope and again instructed the aircraft to go around which was acknowledged. An ILS approach to Runway 15 was then offered which, under the prevailing light wind conditions, the pilots were able to accept and the aircraft landed without further event.
It was noted by the Investigation that at the time of the investigated event, the runway 33 ILS GS had been out of service since 2016 because of unexpected reliability issues which had arisen as a result of work to increase the length of the runway. This meant that the absence of an ILS approach for the airport’s most used runway was unlikely to have been a surprise even to crews making infrequent visits to the to airport.
The Investigation was advised by the operator that the trainee Captain had previously flown non-precision approaches without difficulty and also noted that earlier in 2020, the instrument panels in the aircraft involved had been modified and some instruments had changed position.
Based on the limited available evidence, only the vertical profile had been mis-flown. It was considered that the flight crew had (assuming they were referring to the correct procedure plate) despite warnings from ATC, been mistakenly expecting to intercept a glide slope. It seemed at least possible that on the second approach the crew may have intentionally commenced a premature descent when in IMC confident that the flight would be in VMC well before the MDA. It was also possible that “the apparently routine nature of ATC height and distance checks may have given the pilots the impression the aircraft was descending in accordance with the correct profile”. It was of significance that the supervising Training Captain had chosen not to intervene which he would have been expected to do if he had considered that the trainee Captain’s deviation from the correct vertical profile was inappropriate or unsafe.
It was concluded that “early and unequivocal intervention from those able to see the aircraft was not on the correct profile would have been appropriate”. More generally, it was noted that “non-precision approaches are becoming less common and pilots may be less current in flying them”.
The Final Report of the Investigation was published on 13 May 2021. No Safety Recommendations were made.