Glideslope & noise
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Glideslope & noise
From a curious pax and interested observer of the arguments for and against the 3rd runway at Heathrow:
I have been told that at City aiport a steeper angle of approach is used for noise reasons. If so why is this not used at an airport such as Heathrow and if it could be what sort of reduction in decibels can be expected over the sort of distance typically used for finals into Heathrow flying east to west?
I have been told that at City aiport a steeper angle of approach is used for noise reasons. If so why is this not used at an airport such as Heathrow and if it could be what sort of reduction in decibels can be expected over the sort of distance typically used for finals into Heathrow flying east to west?
In a nutshell it's not used at LHR (and most other airports) because the bigger aircraft are "built" to fly a roughly 3 degree glideslope - just about the worldwide standard. A 3 degree slope for most types gives you a lowish power setting but not such a low setting that the engine is running so slowly it takes a long time to power up should you need it. Flying anything much steeper means flying the approach with the power back at or near idle and gives a high rate of descent near the ground ( especially on the heavy jets with highish approach speeds)...the guys and girls that fly into LCY are not flying heavies, and may have specially modified aircraft/software/procedures.
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It amused me that when the Partenavia (A piddling little six-seat light piston twin) was approved for LCY it needed a far higher power setting to achieve the steep approach required as it was necessaryto use full drag flap setting than it needed with an intermediate flap setting when doing a normal 3 degree approach. Admittedly the noise footpring must have been much smaller because of the steepness of the approach but it certainly made much more noise at low level!
P.P.
P.P.
From my days on the commercial side, I seem to recall that it was noise. It was, IIRC, 7 degrees right from the start, and there were a lot fewer obstacles in those days. Come to that, a lot less passengers as well...
Meanwhile,
"Airplane Seconds From Disaster Near Canary Wharf"
www.flickr.com/photos/birdlike/346725016
"The stricken plane barely missed a building where "The Sisters Of Posterior Cleavage", Nuns of a little-known religious "construction order", were working on an extension to a hospital and orphanage.
Aviation experts suspect that discarded ice from a gin and tonic may have contaminated the petrol, a child using MSN Chat in South Ockendon may have inadvertantly typed "Fokker", paralysing the aircraft's Windows 98 "flying wire" systems, or the pilots may have been distracted by polaroids of the Chief Pilot, taken in a Humberside bed and breakfast in 1991. Other investigators suggested that the doomed craft had inadvertantly lined up with a high-speed exit at nearby Heathrow".
(Did anyone else get bored with the 'MM ballyhoo? :-) )
By the way, this chap's photos of London City ops are outstanding, as, indeed, are his others. Not typical "airliners.net" spotter fodder...
r
Meanwhile,
"Airplane Seconds From Disaster Near Canary Wharf"
www.flickr.com/photos/birdlike/346725016
"The stricken plane barely missed a building where "The Sisters Of Posterior Cleavage", Nuns of a little-known religious "construction order", were working on an extension to a hospital and orphanage.
Aviation experts suspect that discarded ice from a gin and tonic may have contaminated the petrol, a child using MSN Chat in South Ockendon may have inadvertantly typed "Fokker", paralysing the aircraft's Windows 98 "flying wire" systems, or the pilots may have been distracted by polaroids of the Chief Pilot, taken in a Humberside bed and breakfast in 1991. Other investigators suggested that the doomed craft had inadvertantly lined up with a high-speed exit at nearby Heathrow".
(Did anyone else get bored with the 'MM ballyhoo? :-) )
By the way, this chap's photos of London City ops are outstanding, as, indeed, are his others. Not typical "airliners.net" spotter fodder...
r
Last edited by Midland 331; 6th Feb 2008 at 15:53.
LCY 5.5 deg glidepath is due to obstructions; nothing to do with noise.
According to ICAO Doc 8168, a 'normal' glidepath can be anywhere from 2.5 to 3.5 deg, but for Cat 2/3 ILS it MUST be 3 deg.
According to ICAO Doc 8168, a 'normal' glidepath can be anywhere from 2.5 to 3.5 deg, but for Cat 2/3 ILS it MUST be 3 deg.
