1. Commercial aircraft operation engine realibility & safety
18/09/2018
AoA Transport Lunch Seminar
Commercial aircraft operation engine realibility & safety
Olivier Petit & Henrik Ekstrand
Applied Mechanics department, fluid mechanics division

2. Background There is a market pull to fly further and further away.
Average of – planes in the sky at any time. (expected 5% per year increase for the coming 10 years)
Need for regulations to avoid accidents, and manage take-off and landings.
Creation of highways in the sky to avoid collision.
18/09/2018
AoA Transport Seminar

3. Aviation safety
A wide topic where interaction typically occurs between all stakeholders (e.g. Airspace Users (AUs), Air Navigation Service Providers (ANSPs), Airport Operators etc.).
Airspace Users typically has great redundancy in various systems (e.g. three hydraulic systems).
Communication, Navigation & Surveillance (CNS).
ANSPs and AUs are using various surveillance systems for traffic sequencing and separation, including airborne anti collision systems such as the Traffic Collision Avoidance System (TCAS).
Satellite navigation used as primary navigation source associated with very high accuracy.
Communication is established all around the world via ground stations or SatCom.
18/09/2018
AoA Transport Seminar

4. 1953 data from ICAO(International Civil Aviation Organisation)
Early airplanes were powered by piston engine. The reliability of piston engine at the time was rather poor.
There is a close correlation between engine failure and engine power (see left picture).
As a consequence, a 60 minute rule was established In 1953: to always operate an aircraft within 100 NM from an adequate airport (100 NM ≈ 60 min flying with one engine inoperative).
1 NM (Nautical Mile=1.852 km)
Probability of failure for piston engines vs. power at a constant engine speed of rpm.
18/09/2018
AoA Transport Seminar

5. Reliability of jet engines since the 1950s and onwards
The introduction of jet engines significantly enhanced the reliability and safety of propulsion systems.
The failure probability of a jet engine in neither affected by the thrust nor by the size of the engine.
In today’s operation it is possible to operate > 180 minutes from an adequate airport with a twin engine aircraft (based on single engine operation).
18/09/2018
AoA Transport Seminar

6. ETOPS certification: Extended-range Twin engine OPerationS
ETOPS certification operational since 1985 (ETOPS-90, ETOPS-120)
ETOPS definition: extended range operations are those flights conducted over a route that contain a point further than one hour flying time at the approved one-engine inoperative cruise speed (under standard conditions in still air) from an adequate airport.
Combined safety measure, EROPS: En Route Alternate Airports. It denotes that this airport is adequate for use as an ETOPS alternate (weather, runway length, wide and strength…). Military airports are available as En Route Alternate.
ETOPS certification representation
Thule in Greenland, Keflavik in Iceland, Gander in Canada
Airbus A300 twinjet aircraft had been operated across the North Atlantic, the Bay of Bengal and the Indian Ocean under a 90-minute ICAO rule since However, ETOPS officially began in 1985 with the newly issued ETOPS criteria.
18/09/2018
AoA Transport Seminar

7. Operational impact Direct route = 4350 NM 60 min rule = 5700 NM
120 min operation
180 min operation
Direct route = 4350 NM
60 min rule = 5700 NM
180 min rule = 4350 NM
18/09/2018
AoA Transport Seminar

8. Engine certification
There are hundreds of tests that need to be performed for certification of a turbine engine.
Amongst them are:
Maximum static thrust tests
Vibration tests
Endurance tests
Water ingestion test
Hail ingestion test
Ice cloud test
Bird strike test
18/09/2018
AoA Transport Seminar

9. Engine certification: electronic code of federal regulations:
18/09/2018
AoA Transport Seminar

10. Engine certification:
electronic code of federal regulations:
18/09/2018
AoA Transport Seminar

11. Aviation statistics
You can travel 7 times to the moon or times around the globe before experiencing an emergency landing to En Route Alternate Airports.
There were four accidents resulting in passenger fatalities in 2015, all of which involved turboprop aircraft, with 136 fatalities. This compares with an average of 17.6 fatal accidents and 504 fatalities per year in the previous five-year period ( ).
Boeing Statistical Summary of Commercial Jet Aircraft Accidents
IATA: International Air Transport Association, trade association for the world’ airlines
18/09/2018
AoA Transport Seminar

12. Thank you for your attention!
18/09/2018
AoA Transport Seminar