"On the plane Captain is Lord of the Lords. The Captain makes a decision in base of responsibility"

A case study on the conditions for decision-making

The forced landing of the URAL Airlines Airbus A320 on 12 September must be seen as a real feat by the two pilots, and beyond the doubts about their "making decision" and the geopolitical context, we must pay tribute to them for what they achieved.

Like Chesley Sullenberger, who successfully ditched his plane on the Hudson River in 2009, they brilliantly fulfilled their fundamental mission to save their passengers and the plane. And like Sully, they necessarily did so calmly and in cold blood.

Sullenberg had no choice, and he understood this immediately, so the question arises as to what options the URAL Airlines pilots had.

The fact is that they had a hydraulic failure on the green circuit, a simple failure flagged up by a master caution (which did not require any immediate action) apart from carrying out the ECAM ACTIONS, i.e. switching off the green circuit hydraulic pump (EDP) and the Power Transfer Unit (PTU). The consequences for landing were the loss of reverse on the left engine and the loss of nosewheel steering, without affecting braking. On the other hand, a key point is that in the event of a go-around, retraction of the landing gear is no longer possible, so it must not be attempted, and the crucial consequence is that the landing gear remains extended but with the doors open... resulting in a fuel penalty of 180%!

While watching the flightradar24 replay of URAL Airlines arrival at OMSK let’s get the situation awareness as if "thinking from the left seat".

About fuel on board (FOB): The flight was routine with no unusual events, which means that according to the OPS flight plan FOB should be 4600 kg. The minimum fuel required for a diversion is 3700. This also means that the pilot in command has 900 kg, or about 20' of flying time, before he is obliged by the rules to divert to Novosibirsk alternate airfield if landing at OMSK proves impossible.

On the other hand, if he is sure that it is still possible to land at OMSK, he can decide to convert his diversion reserve (2600 kg) into additional holding time, i.e. a good extra hour. Obviously, this decision can't be made if a failure condition affects the landing performance in terms of runway length in such a way that it would be insufficient. For example, a dual hydraulic loss would require a minimum runway length of 2800m, whereas OMSK has only 2500m. In contrast, landing performance at OMS is not affected by the loss of the single hydraulic green circuit, in the sense that the runway length remains sufficient despite the loss of left reverse and the possible lack of spoilers (1 & 5).

All failures that affect the nominal aerodynamic characteristics of the aircraft will also increase its fuel consumption.

The captain, in his interview by investigators stated he estimated 900 k of fuel remaining at Novosibirsk what suggested he considered a fuel penalty factor of 25%, investigators said. According to Airbus procedures, the fuel penalty factor allows the calculation of an additional fuel to the nominal quantity, i.e multiplying this nominal quantity by 1,25 (fuel penalty factor of 25%). With a minimum diversion fuel of 3768, the fuel requirement for a diversion in these conditions increases to 3768 times 1.25 = 4710.

However, according to the airline, the fuel on board at go-around was only 4200, and the required alternate trip fuel was 2618 times 1.25 = 3272, giving a remaining fuel in Novosibirsk of 927. On this point the captain's statement appeared to be correct.

Unfortunately, it didn't work and the plane was forced to land in a field.

This can only be explained by either an aerodynamic degradation of more than 25%, or a lower than declared fuel quantity at go-around, or a combination of both.

What else could have caused such a deterioration in the aerodynamic characteristics of more than 25%, apart from the landing gear remaining extended, resulting in a fuel penalty factor of 180% ?

In that case the nominal alternate trip fuel increases to 2618 times 2,8 = 7330 kg. So the lack of fuel was 3130 kg ... Slightly less than half the required amount of fuel was missing. This is consistent with the fact that the flight ended more than halfway through.

The commander couldn't have been unaware that the landing gear had remained down, otherwise why would he have respected the speed limits with the gear down? So it's highly unlikely that he actually assessed the fuel requirements in those conditions. How could he have decided to fly to Novosibirsk knowing that he was almost half out of fuel? Whereas his remaining fuel would have allowed him to fly over OMSK for at least 40 minutes.

What was his compelling reason for diverting, given that he was not prevented from landing at OMSK by the Green Hydraulic failing?

But what caused the missed approach ?

The aircraft was not in the final approach, which begins at 4 Nm from the threshold, it was still at 7 Nm when he cancelled the approach and turned left in the downwind leg, although it appeared to be fully ready for the final approach (stabilized on the localiser at approach speed). We can only deduce that an ECAM alert occurred and that he immediately switched to standby downwind and carried out the ECAM actions and decision making

In fact, he decided to divert to Novosibirsk almost immediately. This is what the flightradar24. replay and the radio communications show. He certainly didn't take any time to assess the situation in terms of fuel in the configuration, as he made his decision to divert in less than 3 minutes.

The best evidence of this is provided by the radio exchanges: SVR1383 was cleared to FL70, acknowledged receipt and OMS Tower then asked

• 1383, ready to copy Novosibirsk weather?

It was only then that the commander became concerned about the amount of fuel needed to reach Novosibirsk.

• Ready, and give us a heading please, let's see how much fuel we need !

It can be admitted that, knowing in one way or another that he should not wait at OMSK, he chose to check fuel en route to Novosibirsk, but it was then imperative to do so as quickly as possible in order to be able to return to land at OMSK if diversion to UNTT proved impossible.

"The Fuel Penalty Factors provided in the QRH tables are given as a guideline. The flight crew should confirm this Fuel Penalty Factor by monitoring the actual fuel consumption."

If fuel systems have proven their reliability, in case of failure, the ultimate safety barrier to avoid finding oneself in a fuel critical situation is fuel monitoring by the crew.

During the flight, fuel checks mainly aim at detecting any abnormal consumption, be it due to a leak or unanticipated drag (e.g. spoiler or landing gear, slats or flaps not fully retracted) or any other reason.

Indeed, such situation would make the FMS fuel predictions too optimistic and potentially lead to fuel exhaustion in flight.

One of the easiest ways is to quickly calculate the consumption per nautical miles, which expresses the nautical miles flown per unit of fuel and is given by a simple formula " Cd = Fuel flow rate / ground speed." Then dividing the FOB (fuel on board) by this Cd gives the distance that can be flown ... to compare with the remaining distance to the destination... The so-called Specific range (Rs) is 1/Cd, then the distance that can be flown is given by d = Rs times fuel on board

• Let's estimate the real specific range of the SVR1383 and the real penalty factor. The nominal trip fuel is 2918 kg for 320 NM, i.e. 9,12 kg/Nm.
• The published ADS-B data allows easy measurement of the actual distance flown from the decision to abort the approach to the landing in the crop field, which is approximately 270 Nm. In reality 4000 kg were burned for 270 Nm, i.e. 14,81 kg/Nm. We can therefore deduce a real fuel penalty factor of 62%. (14,81 / 9,12 = 1,62)The real specific range was thus 67,5 Nm/1000 kg (1 / 14,81 = 0,0675), which unfortunately means that SVR1383 couldn't fly more than 284 NM with 4200 kg of fuel on board.
• A320 FCOM provides tables for special operations with gear down. Taking into account the 15% "all landing gears doors are extended" penalty factor, the fuel burned by SVR1383 for the climb to FL180 can be estimated at 1250 kg. This means that the fuel on board on arrival at FL180 was approximately 2950 kg for a climb of 60 Nm. The tables also show the specific cruise range: 61.2 Nm / 1000 kg, given the 15% fuel penalty factor. At FL180 the available fuel on board was about 2950 kg, the aircraft couldn't fly more than 2,950 tonnes times 61.2 = 180.5 Nm ...Thus, using the table "Special operations with gear down" and "all landing gears doors are extended", the aircraft cannot fly more than 240 Nm (including climb), while the alternate distance is 320 NM.

Most likely, the nose landing gear remained extended, as well as the doors, and perhaps the nose wheel was left at 90°...