Preventing Fan Cowl Door Loss

Since the previous article published in July 2012, 14 events of loss of fan cowl doors during flight were reported to Airbus (12 events on A320, one on A330 and another on A300 aircraft). 

The aircraft had undergone overnight maintenance and, in most of the cases, the fan cowl doors were opened to check the Integrated Drive Generator (IDG) oil level. The morning of the incident, the walkaround inspection did not reveal the opened fan cowls.

Airbus developed several additional devices to prevent fan cowl door loss events by enhancing the prevention means and reducing the number of fan cowl doors openings required by scheduled maintenance. 

An improved latch with a key and a “REMOVE BEFORE FLIGHT” flag attached to the key (fig.1) has been introduced in December 2015 on the A320ceo aircraft. The key is needed to open the latch. When the fan cowl door is opened, the key remains on the latch. It can only be removed if the latch is fully closed. When not used, the latch key has to be stored in the cockpit with the landing gear pin.

The following Airworthiness Directives (ADs) mandate the retrofit of this new lockable latch on A320ceo aircraft equipped with IAE and CFM56 engines:

A330neo aircraft equipped with RR Trent 7000 engines are also fitted with this latch key device from production line.

Proximity sensors located at each latch monitor the fan cowls position on A320neo aircraft equipped with PW1100 and LEAP-1A engines. The ECAM displays the ENG1(2) FAN COWL NOT CLSD caution if the fan cowls are not properly closed.

In addition to the cowl position monitoring, a prevention flag extends mechanically from the surface of the left hand fan cowl when the forward latch is opened to warn the ground personnel and the flight crew that the latch is not closed (fig.2) on A320neo equipped with CFM LEAP-1A engines.

(fig.2) Mechanical prevention flag on an A320neo equipped with LEAP engines

A U-arrestor device holds the fan cowls in a partially open position when the cowls are lowered on A340 equipped with TRENT 500 engines and on A330neo with TRENT 7000 engines. It is obvious to the operator that the cowls are not fully closed when looking from below or from the side of the cowl. The U-arrestor pin must be pressed to close the fan cowl door (fig.3).

The equivalent function is insured by the “Hold Open Device”, mandated by the AD 2001-381(B), requiring embodiment of the SB A320 71-1028 on A320ceo equipped with V2500 engines.

It is insured by a similar “Push Open Device” on A320neo equipped with PW1100G.

Airbus recommends the use of a “LATCH COWL BEFORE FLIGHT” red flag when the fan cowl doors are unlatched on A300-600, A310, A330ceo, A340, A340-500/600 aircraft. This flag can be obtained with the following SBs:

• SB A300-600 71-6030
• SB A310 71-2039
• SB A330 71-3034
• SB A340 71-4009
• SB A340-500/600 71-5005

If the fan cowl door latches are left open on the A350 or A380 aircraft, the latch access panel cannot be closed. This will be visible to ground operator or flight crew during an exterior walkaround check (fig.4).

Additional markings with arrows pointing toward the latches (fig.5) are there to remind the ground staff to check the latches are engaged and correctly secured on A320ceo aircraft. They can be installed through:

• VSB RA32071-161 on CFM56-5A/5B
• VSB NAC-71-0330 on IAE V2500

These are optional SBs and therefore they are not installed on production aircraft.

Decals with cautions located at eye level ensure that fan cowl doors are closed and correctly latched before flight (fig.6) on A320 aircraft. They are installed on recent A320ceo production aircraft and on A320neo. They can also be installed by retrofit with the following VSBs:

• VSB RA32071-117 on CFM56-5A/5B
• VSB NAC 71-0235 on IAE V2500

Airbus revised the AMM TASK “Opening/Closing of the Fan Cowls” on all Airbus aircraft to introduce a logbook entry that informs the flight crew that the fan cowl doors have been previously opened. This will alert the flight crew that they should confirm that the fan cowl doors are correctly closed during their exterior walkaround.

Additional technical solutions were also developed to reduce the number of fan cowl doors openings.

An optional IDG access door is available on A320ceo aircraft equipped with CFM56-5A/5B engines. IDG oil level can be checked via this access door without opening the fan cowl doors. A320neo LEAP, A330ceo RR Trent 700 and A340-500/600 RR Trent 500 are already equipped with this IDG access door (fig.8).

To reduce the frequency of fan cowl door opening for aircraft not equipped with the IDG access door, Airbus demonstrated that the IDG oil level check interval could be extended from 150 FH to 300 FH (or 2 months) on CFM56-5A/5B and IAE V2500 engines.

A Remote Oil Level Sensor (ROLS) monitors the IDG oil level and an IDG LOW OIL LEVEL ECAM alert will appear when servicing is required. With this monitoring, the inspection interval is longer (fig.9).

(fig.9) Summary of maintenance solutions

To improve the latch visibility, they are covered with fluorescent paint. The condition of the paint on the latches needs to be checked every 7 500 FH (or every 24 months) on A320ceo aircraft in accordance with the Maintenance Planning Document.

Airbus updated the exterior walkaround section of the FCOM Standard Operating Procedures for all aircraft by introducing additional steps in the walkaround (fig.11). This change requests that the correct latching of the fan cowls is now checked from both sides of each engine.

The exterior walkaround is one of the last opportunities to detect incorrectly latched fan cowl doors before flight. The flight crew must pay particular attention to check the fan cowl doors are correctly latched.

The most effective way to confirm that all latch handles are correctly engaged and flush with the fan cowls is to crouch down to get a good line of sight with the latches. The flight crew needs to check on both sides of the engine to confirm there is no gap around the cowl and all latches are secured (fig.12 and fig.13). Use a torch light if the lighting conditions are poor or if the inspection is done by night.