Aircraft safety - a question
Discussion
Silver993tt said:
gtr-gaz said:
In light of the recent near air disaster in New York, I would like to know why they do not fit some sort of grill over the engine intakes to prevent objects getting sucked in?
There must be a good reason not to do it!
air flow.There must be a good reason not to do it!
and what would you propose to make it from too?
Grilles are fitted to some aircraft (although AFAIR not commercial stuff) the one that springs to mind being the Mig-29, it has them so it can take off from unprepared runways, i.e. s
te on them! 
Even if you could fit them to a commercial aircraft (completely discounting the loss of thrust through airflow, as mentioned) it wouldn't have stopped the bird strike that aircraft had.
te on them! Even if you could fit them to a commercial aircraft (completely discounting the loss of thrust through airflow, as mentioned) it wouldn't have stopped the bird strike that aircraft had.
Early jets sometimes were fitted with grilles - e.g. early Messerschmitt Me262 and Heinkel He280s . However, a grille actually blocks quite a bit of air from entering the intake - and it creates distubances and eddies which would prevent the engines from functioning correctly. I am also pretty sure that many grilles would have trouble standing up to the suction power of a modern 50,000 to 90,000 lbs thrust engine (the engines on early WW2 jets barely reached 2,000 lbs thrust).
Edited by Eric Mc on Sunday 18th January 12:38
LukeBird said:
Grilles are fitted to some aircraft (although AFAIR not commercial stuff) the one that springs to mind being the Mig-29, it has them so it can take off from unprepared runways, i.e. ste on them!
Even if you could fit them to a commercial aircraft (completely discounting the loss of thrust through airflow, as mentioned) it wouldn't have stopped the bird strike that aircraft had.
I'm sure EricMC or another will either confirm or correct me, but from my recollection the MiG29 had a flap that shut off the main intake and opened one up from on top of the intakes for use on ill prepared runways, no grills - effectively a 2nd intake system.te on them! Even if you could fit them to a commercial aircraft (completely discounting the loss of thrust through airflow, as mentioned) it wouldn't have stopped the bird strike that aircraft had.
The danger of a grill working loose in flight and being sucked into the engine is too imense.
also, a bird the size of a goose hitting any kind of grill at say 300mph just after take off would be a huge collision force that would more than likely destroy the grill which would also then enter the engine. Big bits of metal entering the engine would cause alot more damage than bird flesh (which is clearly bad enough).
The only jet aircraft with grills I can recall are helicopters, the Pumas used sand and dust filters and we regularly used grills on the Wessex SAR though since they are driving through a gearbox not hi-bypass engines where much of the thrust is derived from the fan in front of the engine that was acceptable. There was a noticeable perfomance penalty though even for these types of engines.
Other times they would be used was doing ground engine runs to prevent ingestion of nuts, bolts, mechanics whatever.
Other times they would be used was doing ground engine runs to prevent ingestion of nuts, bolts, mechanics whatever.
Mutley said:
LukeBird said:
Grilles are fitted to some aircraft (although AFAIR not commercial stuff) the one that springs to mind being the Mig-29, it has them so it can take off from unprepared runways, i.e. ste on them!
Even if you could fit them to a commercial aircraft (completely discounting the loss of thrust through airflow, as mentioned) it wouldn't have stopped the bird strike that aircraft had.
I'm sure EricMC or another will either confirm or correct me, but from my recollection the MiG29 had a flap that shut off the main intake and opened one up from on top of the intakes for use on ill prepared runways, no grills - effectively a 2nd intake system.te on them! Even if you could fit them to a commercial aircraft (completely discounting the loss of thrust through airflow, as mentioned) it wouldn't have stopped the bird strike that aircraft had.
The danger of a grill working loose in flight and being sucked into the engine is too imense.
Yeah it completely closed the intakes, and the bleed valves were just over the leading edge of the wing root.
I guess they heavily inflicted take-off length, but a bit safer than the engine ingesting a lump of concrete!
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