Dissection of a Hard Landing at London City
It was the morning of the 18th of August 2007 in London. The aircraft was HB-IYU, an Avro RJ100, the improved version of the British Aerospace 146 short-haul airliner, with four turbofan engines and a retractable tricycle landing gear (the most common landing gear for modern aircraft). The captain had over 9,000 flying hours, of which 1,340 were on type. The first officer was pilot monitoring.
The flight was a scheduled passenger service from Zurich to London City Airport. The weather forecast was for short periods of rain and southerly winds of 10 knots, so pretty much as good as it gets in London. The runway length required for the aircraft that day using a steep approach was 1,066 metres (3,500 feet). London City has a concrete runway of 1,500 metres (4,900 ft).
As the RJ100 approached London City using the ILS approach, everything was normal. At 3,000 feet, the flight crew initiated the glideslope capture, lowered the landing gear, set the flap to 33° and deployed the airbrake.
The captain disconnected the autopilot at 1,300 feet. As they came in, the flight crew monitored their approach using the PAPI lights and noted that they were slightly high.
The first officer was monitoring the airspeed relative to the target speed at which the aircraft should cross the runway threshold (VREF). As they passed through five hundred feet, he called out the relative speed: +7, +3, +1, +3 and +4.
These figures meant that they were below the target speed as they passed through 500 feet above ground level. Please see John’s comments below regarding the call outs, which at this stage appear to have shown them as coming slightly fast.
The Extended Ground Proximity Warning System (EGPWS) called out FIFTY: the altitude of the aircraft was 50 feet above ground level. The first officer called out “+2” and then “+1” right after the EGPWS announced 50 feet above ground level. The power levers were pulled back to idle.
As a part of the final approach, the Pilot Flying executes the “landing flare” where the thrust levers are at the idle position and the nose of the plane is raised slightly. This slows the descent rate and positions the aircraft in the proper attitude for the landing. For a tricycle landing gear, this means that the aircraft touches down on the main landing gear with the nose wheel touching down after the aircraft is stable and reduced in speed. For a steep approach, which is required for London City, the pitch attitude of the aircraft would be around 4°. The flare height for an aircraft of that size is around 30 feet, so the Pilot Flying was either flaring or about to flare.
The Automatic Terminal Information Service (ATIS) at the time of the landing cited the wind as “surface wind from 190° at 11 knots” however, an aircraft which landed twenty minutes later said that he found the approach much more turbulent and difficult than he expected.
Just before the EGPWS call for 30 feet, the flight crew felt the aircraft suddenly drop. The captain immediately responded by pulling back on the control column to avoid a hard landing.
As a result of the increased pitch, the rear of the aircraft touched the runway. The flight crew were not aware that they’d suffered a tail strike and were not initially clear on what had destablised the aircraft.
Here’s the video taken by a plane spotter filming at London City.
An inspection of the runway showed that the first contact was the rear galley drain pipe, which left a five-metre long scrape starting at the PAPIs and just to the right of the runway centreline. Then the lower rear fuselage scaped the runway for another eleven metres. Based on the touchdown speed of 113 knots, the rear section of the aircraft was in contact with the runway for 0.24 seconds. It was enough.
The aircraft came to a safe stop. There were no injuries.
The flight data recorder showed that there was a slight headwind until approximately 50 feet above ground level, at which point it became a variable and slight tailwind. It only captures the information every four seconds but the data did not appear to show evidence of gusty conditions. The aircraft was descending at 900 feet per minute and reducing smoothly. The flight data recorder did not show any sudden drop in altitude.
This was not the first Avro RJ100 to suffer a tail strike at London City. The manufacturer carried out an investigation after this incident and determined the following key factors.
- The aircraft speed was below the final landing approach airspeed target (VREF), which meant the final approach required a high angle of attack.
- A high rate of descent which meant that a higher pitch attitude was required in the flare.
- Excess speed leading to the aircraft floating and a high pitch attitude on touchdown.
The accident investigation looked at these factors and that the tail strike events are clearly a result of various circumstances which lead to excessive pitch attitudes at touchdown. They concluded that for a successful steep approach for a relatively short runway such as the runway at London City, a high degree of accuracy is required.
Although the aircraft was stable and had made a good approach, the call outs from the Pilot Monitoring made it clear that the aircraft was generally below the target speed by one to five knots. The Flight Data Recorder confirmed this, showing the aircraft at four knots below target speed at 50 feet and 35 feet above ground level. As the thrust levels were pulled back to idle, the airspeed decreased again caused by the shift of the headwind to a tailwind.
These minor changes all reduced the energy of the aircraft. This was the apparent drop that the pilots felt. The commander pulled back to avoid the hard landing, which brought the pitch attitude to 9.3° as they touched down, steep enough to cause the tail to strike the runway.
From the report:
Another operator of this aircraft type, who had previously experienced several tailstrikes at LCY, introduced revised training and procedures for their pilots. One element of this was to introduce an SOP monitoring call of ‘ATTITUDE’ if a pitch angle of 5º or greater is seen during the flare. If this call is made, then the pilot flying must not increase pitch but is required either to accept the pitch attitude for landing or to go around.
Since this accident the operator has undertaken a re‑assessment of the risk level of its operations into LCY. A further review of procedures and training requirements for LCY has also been completed. Some changes to SOPs have been implemented and an additional training programme for LCY has been incorporated into the recurrent simulator schedule.
In other words, this mistake was way too easy to make in that aircraft at that airfield.