On 6th August 2021, Qatar Airways Boeing 777-200 performing flight QR677 from Male’ to Doha returned mid-flight due to a windshield crack.
The crew declared emergency, descended to 10,000ft, and safely landed at Velana International Airport around 50 minutes later.
How can a cockpit windshield crack?
Cockpit windshields are built with multiple plies of glass or stretched acrylic material to be able to withstand enormous stress.
Similar to fuselage or engine tests, cockpit windshields undergo rigorous testing including pressure changes, temperature control, and bird strike tests.
The windshields area is also tested for chemical resistance to hydraulic fluid or jet fuel as well as abrasion including rust or rain erosion.
Windshields can crack while in flight for various reasons:
As windshields are required to be heated at higher altitudes due to lower outside temperature, an uneven heating or a short circuit induce intensity can change & break due to differential pressure inside & outside the cabin.
A substandard windshield of a lower quality can deteriorate at a faster rate and form a crack.
Damage suffered during installation or repair can also contribute to a crack during flight.
Windshields can be damaged while in flight by being hit by a bird at lower altitudes or by hailstones.
Windshield for a jet aircraft can cost between USD 25,000 to USD 40,000 and has a service life of 10 years.