What pilots should do after a drone hit?

General

Statistics reveal that majority of bird strikes occur below 500ft AGL and out of which 25% cause damage to aircraft. In 80% of bird hit cases, the major damage is sustained by windshield, radome, nose or engine. This is very logical.

These damages lead to increased operational costs in terms of flight delays (RTO or IFTB or diversion), engine damage (mostly fan blade damage or increased vibrations), reject take offs or increased fuel consumption due to increased drag.

Similarly drone hits are more likely close to ground during approach landing and take off phase overflying urban ares but will not be limited to that. As brought out in previous article the drone hit is likely to cause more severe damage.

Pilots course of action.

Drone hit is confirmed, if the crew:

• Sees drone flying very close by and hears a loud thud noise
• Along with that secondary indications could be temporary or permanent changes in the engine parameters, or change in engine noise or change in flight instrument readings or their reliability when compared with other instruments. These secondary indication may or may not be present depending on place of hit.

This possibly could occur during various phases of flight but the most catastrophic would be close to ground and hence we will discuss these situation one by one.

On take off roll

Speed below 80 Kt.

• A rejected takeoff at low speed has no serious consequences and may be contemplated for any suspected or confirmed drone strike. The aircraft may continue after integrity check at ramp leading only to delay and avoiding possible disruption.

Speed above 80 Kt and below V1

• A takeoff at high speed should be rejected only in case of confirmed hit. Action must be taken quickly to ensure a complete stop before the end of the runway.

Above V1 and Takeoff

• Flight crews must be prepared for all contingencies. A thorough briefing prior to every take off is the most effective tool to combat such situation and prevent CRM degradation.
• Golden rule - All action to be taken above safe altitude and in stable flight conditions.
• Analyse secondary indications to confirm area of hit or ask cabin crew members to conduct visual inspection to confirm damage if any.
• Due to higher engine speed during the phase any hit on engine is likely to cause more damage. All changes to engine should be kept to minimum and done very smoothly and gradually to avoid engine surge or flame out.
• Drone strike to engine is more likely to cause complete flame out, fire or vibrations along with high EGT.

At Landing

• On short final, do not go around, if drone hit is encountered. Do not make abrupt changes and maintain the parameters.
• The use of reverse thrust on landing after a drone strike should be avoided. It may increase engine damage, especially when engine vibration or high EGT are indicated.

Happy landing. Be safe.