Description

On 4 December 2023, a Boeing 737-8200 (EI-HET) being operated by Ryanair on a scheduled international passenger flight from Klagenfurt to London Stansted with the Captain as PF commenced a go-around at destination from significantly above decision altitude in day IMC after a mismanaged and unstable ILS approach. The go-around continued significantly above the missed approach stop altitude until alerted to the error by ATC but the recovery then involved a second level bust at a very high rate of descent with an EGPWS Mode 1 Warning occurring as recovery climb was initiated. Once finally level at 3,000 feet, the arrival was completed without further event.

Investigation

A Field Investigation was carried out by the UK Air Accident Investigation Branch (AAIB). The CVR and FDR were isolated by the operator immediately after the flight and were subsequently removed from the aircraft along with the EGPWS and all relevant data was downloaded. Relevant recorded ATC radar information was also available and used in conjunction with data from the onboard recorders.

It was noted that the 46 year-old Captain had of a total of 5,300 hours flying experience which included 2,800 hours on type. Time in command on type was not recorded but he had been with the Operator for four years. Similar experience and age information for the First Officer was not recorded but he had been with the Operator for two years. Both pilots were based at London Stansted and therefore very familiar with it. The training records for both pilots showed that they had completed a large number of go-arounds during simulator training with the Operator (the Captain “at least 73” and the First Officer “at least 46”). In the Captain’s case, these had included a ‘High Energy Approach Recovery’ involving a similar scenario to that presented by the investigated event although he stated that it had been his first in an aircraft as PF.

What Happened

With the Captain as PF, the approach brief was given for radar vectors onto a Cat 1 ILS approach to runway 22 at Stansted and a flap 30 landing. A surface wind of 130°/12 knots and an overcast at 400 feet agl was noted. Once working Stansted APP/DIR, clearance to FL080 and then 6,000 feet QNH was given and actioned with a single AP and the A/T engaged and LVL CHG mode used. Passing the equivalent of about 7,800 feet aal and maintaining 235 KCAS, ATC advised there was about 24 nm to run.

Shortly after this, the controller reported having noticed that the flight was a bit high and gave a radar heading which would provide extra track miles. As the flight approached 6,000 feet QNH with about 15½ track miles to go, the speedbrakes were extended for just over half a minute and clearance was then given to establish on the LOC and shortly thereafter to continue descent to 2,000 feet QNH and to descend further on the ILS. Once inside 12nm, a speed reduction to 180 KIAS was given. As the LOC was captured when passing 3,683 feet aal the speed was still 195 KCAS with about 9 nm to go and flaps 5 selected. Thirty seconds later with 7 nm to go, the APP controller instructed the flight to reduce speed to 165 KIAS until reaching 4nm and contact TWR. The landing gear was selected down and flap 15 set at 6nm passing 2,650 feet aal with the speed still 186 KCAS. A landing clearance was given at 5nm and the Captain was recorded commenting that “if we don’t catch it [the G/S] we’ll have to go around”.

As the previously cleared descent altitude of 2,000 feet QNH was approached, the altitude acquire began and was annunciated and the Captain responded by re-settimg 100 feet as the selected altitude. This action was quickly followed by the Captain’s decision to go around, ATC being so informed and responding with “Standard Missed Approach” (ahead to ILS DME 3.3 not above 3000 feet followed by a right turn to the Barkway VOR). The go-around was initiated at 1,579 feet aal at 3.6 nm from touchdown and as the AP automatically disengaged, the Captain took over manually following the FD 15° nose up command as the A/T automatically increased thrust to 82% N1 and the First Officer selected the gear up.

As the aircraft passed 2,700 feet QNH, flap 5 was selected and the climb then continued through the 3,000 feet QNH stop altitude. As it passed 3,400 feet at around 180 KCAS, the TWR controller then saw this on his aerodrome traffic monitor and transmitted “maintain 3,000 feet please, 3,000 feet” and received the First Officer’s response “maintaining 3,000 feet Wilco”. The aircraft had reached “a maximum pitch of 16° nose-up, a maximum climb rate of 4,100 fpm and an altitude of 4,030 feet QNH”, before the Captain responded by reversing the pitch attitude to 5 - 10° nose down and “made a nose-down trim input, to initiate a descent, during which 0.40 g was recorded”. The descent was commenced still in manual flight and with the A/T engaged but also with the go-around thrust still set. 

The radar-derived flight path during approach (yellow), go-around and climb level bust (orange) and recovery and the second approach (blue). [Reproduced from the Official Report]

As the aircraft then began to descend, the Captain noticed the selected altitude was still set to 100 feet and so he reset it to 5,600 feet. With the speed increasing through 235 KCAS, the First Officer called “watch yourself…speed…speed” with the Captain responding by extending the speedbrakes and manually retarding the thrust levers to idle but as the A/T was still engaged they advanced back to go-around thrust. Not recognising why this had happened, the Captain again manually retarded the thrust levers to idle but when they advanced again, the First Officer suggested that he should hold them at Idle which the Captain accepted.

Having again failed to level at the 3,000 feet missed approach altitude, the Captain finally pitched the aircraft nose-up achieving a maximum recorded vertical acceleration of 1.89g. As he did so, an EGPWS Mode 1 ‘SINK RATE’ Alert was immediately followed by a ‘PULL UP PULL UP’ Warning. The lowest recorded altitude was 1,740 agl (2,078 feet QNH) overhead the runway. During the descent the aircraft had reached a maximum nose down pitch of 17.7°, a rate of descent of almost 9,000 fpm and a maximum recorded speed of 295 KCAS with Flap 5 still set.

As the recovery from a second level bust was commenced, the A/T was disconnected and the selected altitude was at last set to the 3,000 feet missed approach altitude which was then acquired. The entire sequence of approach, go-around, level bust climbing, level bust descending and recovery to level flight at the missed approach altitude had occurred in IMC.

Once stabilised at 3,000 feet QNH, the AP and A/T were engaged and flap 5 retracted and radar vectors were provided for another ILS approach to runway 22 with an uneventful landing following.

Why It Happened

Fatigue was quickly eliminated as a potential context for the event. The ILS approach procedure in the Operator’s FCOM required that the missed approach altitude should be set once the GS was captured but also envisaged that capture of an ILS GS from above might, at times, occur. It provided specific guidance on how to ensure that - as for any approach - the requirement for a stabilised approach to be achieved by 1,000 feet aal when in IMC (which prevailed during the whole of this event). For the specific case of intercepting an ILS GS from above in such conditions, this guidance included setting the missed approach altitude by 1,000 feet aal i.e. by 1,400 feet QNH for Stansted.

Company procedures for all ILS approaches required that flights must be established on the GS by 5nm which for the Stansted ILS was 1,332 feet aal. At 5nm, the flight under investigation was still significantly above the GS with no closing trend but FDR data showed that the go around was not commenced until 3.6nm from touchdown.

It was observed from the CVR data that “at no point during the approach did either crew member share their mental model as to where they thought the aircraft was on the 3° CDA profile” until the possibility of a go-around was mentioned by the Captain with about 5 nm to go. It was considered that this failure may well have precluded more timely action to correct the descent flight path so that a go-around would not have become necessary.

In respect of the 1,000 feet exceedance of the missed approach altitude, it was suspected that a significant factor was the failure to set this altitude, although it must have been well known to both pilots given that they were based at Stansted and therefore conducting around 50% of all their ILS approaches there. However the there was no proactive or reactive exceedance-related call from the First Officer.

In respect of the second level bust when descending below 3,000 feet, although the First Officer did eventually make the mandatory ‘Speed’ call, this did not occur until the indicated speed was already 40 knots above the OM-specified 195 knots when the speed limit had initially been breached and had thereafter continued to increase.

The narrative Conclusion of the Investigation was as follows:

This serious incident occurred because the Missed Approach Altitude (MAA) was not set in the Mode Control Panel (MCP) before a go-around was performed. It was not set to the MAA because the flight crew were attempting to intercept the glideslope from above. This required the MCP selected altitude to be set to a height below the aircraft, and the MCP selected altitude was not adjusted to the MAA following the decision to go-around before it was executed.

The approach and go-around were flown in instrument metrological conditions (IMC) and hence the pilots had no external visual references. During the go-around the pilot flying was fixated on the Flight Directors and did not recognise that they did not command a level off at the MAA until it had flown through it.

The subsequent recovery manoeuvre from the level bust was probably exacerbated by the thrust levers being moved from a high-power setting to idle resulting in an excessive nose-down attitude, rate of descent and IAS for the aircraft’s configuration. Given the aircraft’s height during this descent the Enhanced Ground Proximity Warning System was triggered just after the commander had initiated a pitch up into a climb back to the MAA.

This serious incident involved a Boeing 737-8200 [MAX] (but) it could have occurred in any variant of the Boeing 737, or any other type of aircraft with similar autopilot and flight director systems. There have been other Serious Incidents with similarities to the EI-HET (event) that have been investigated.

Safety Action
Aircraft Operator Ryanair responded to the event with the following actions:

• Re-emphasised to all pilots the correct go-around procedure via a mandatory learning module.
• Introduced a training package covering high energy approaches and all engines go-arounds to demonstrate non-standard or unexpected go-around conditions.
• Introduced in their ‘summer 2024’ recurrent training package a new FCOM ‘Discontinued Approach’ procedure to ensure correct AFDS (Autopilot Flight Director System) selections and aircraft configuration prior to commencing a go-around above the 500 feet agl stabilised approach call when not in the landing configuration and above minimums.

The Final Report was published on 21 November 2024. No Safety Recommendations were made.

Related Articles

• Level Bust
• Missed Approach
• Go-Around
• Stabilised Approach
• Decision Altitude
• Energy Management During Approach
• Instrument Landing System (ILS)
• Cross-Checking Process
• Situational Awareness
• Standard Operating Procedures (SOPs)