Visibility @ Stansted this morning...

Discussion in 'Current Affairs, News and Analysis' started by Litotes, Apr 3, 2009.

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  1. On this morning's news broadcasts, I watched Mr & Mrs Obama walk up the steps to Airforce One on a pretty dank and dismal Stansted morning. Visibility looked awful and certainly less than one might need to fly an aircraft.

    However, the party appeared to be on time in Paris. Did Airforce One sit on the ground until it cleared or does Airforce One have aids that permit it to launch in zero visibility?

    Litotes
     
  2. Perhaps they beamed him up to the space station then beamed him down to Paris.
     
  3. Lo,for He is God.Crappy weather shall not stoppeth His progress in enlightening those in perpetual darkness.

    Psalms 374 Verse 37
     
  4. VFR/IFR What was the weather like at CdeG is more importantly
     
  5. Mucking sure if even normal civvy airliners can take off in the pitch black of night, then a spot of Good Old Brit Clag ain't going to stop Superbama.
    john
     
  6. Maybe Stanstead has special facilities in the Met/Control Tower dept. It is the airfield of choice for hi-jacked aircraft (remember when they used to do that?) so they would want to be sure that such a kite would get in to land.
     
  7. Low Visibility Operations (LVOs) are commonplace in commercial operations.

    To conduct LVOs the airport needs to be certified in terms of lighting and ILS (Instrument Landing System) performance. The aircraft need to be equipped with a suitable autopilot and auto-thrust system and the crew need to be qualified for LVOs, which involves both initial and recurrent training.

    I don't know what equipment is fitted to the VC-25 (Air Force One) but an equivalent Boeing 747 with the highest level of LVO certification (known as Category 3B) requires a visibility of 150m for take-off and 100m for landing. These limits are laid down by the civilian aviation authorities and are applicable to commercial operators. The USAF is not bound by civilian regulations and may well choose to operate it's aircraft to even lower limits. There will almost certainly be a minimum visibility for take-off as this is a manual manoeuvre performed by the pilot using external visual references. However, an autoland is a fully automatic manoeuvre and can be performed in zero visibility as the autopilot does not require any form of visual reference to perform a safe landing and rollout. The aforementioned 100m limit is imposed to allow for safe airport ground operations after landing. The USAF may well choose to operate to near-zero visibility for landing, knowing that the airport will be sterile for Air Force One movements.
     
  8. I recall flying back from Belfast to Heathrow,a long time ago.Because we landed in fog,I (and the other SLC)were given either a tie or pen to mark the fact the aircraft landed using some techy stuff.
     
  9. Well if a plane can fly through clouds, which fog is but on the ground and not in the big blue sky, they have a radar thingy. So I guess they can. Pity Crab Air dont!

    Stilts
     
  10. Thanks, Alfie. I knew about automatic landing systems but wasn't aware that they had sorted out take-offs. The "sterile world" of Airforce One will have helped!

    Litotes
     
  11. Spoke to someone yesterday who was one of the many looking after the VC-25 during its visit (amazingly thorough security) and he said that visibility for takeoff was ok by Stansted's normal standards. Aircraft do take off in worse conditions there. However, conditions were not not safe enough for the Presidents helicopters to fly from London to Stansted so he came up by car.
     
  12. Litotes,

    Take-off in low visibility is not really aided by any special equipment. It is performed by the pilot looking out the window and keeping straight along the runway centreline. The normal manoeuvre is very straightforward from a handling perspective; the difficulty only comes if an engine fails. Engine failure during take-off usually causes the aircraft to swing before the pilot fully recognizes the problem and it is just that bit harder to deal with in low visibility. Once the aircraft is airborne the pilot transfers to flying on instruments regardless of the visibility.

    The development of the lowest take-off limits for LVOs are really to do with airport equipment - primarily lighting and visibility measuring devices. For example if the runway does not have a way of measuring Runway Visual Range (RVR) the take-off limit increases to 250m, and if it has no centreline lights it would go up to 300m. Additionally, before an LVO take-off the crew must be able to nominate a point of landing within 2 hours flying at engine-out speed where the weather is good enough not to require LVOs.

    I don't know whether helicopters have any different criteria, but I would suggest that Marine One is only equipped for Cat 1 instrument approaches. In an aeroplane this requires 550m visibility and the pilot must achieve visual contact with the runway by 200ft above the ground. It is likely that Marine One could not get into Stansted for this reason.

    RAF transport aeroplanes operate to approximately the same take-off criteria as I mentioned before (150m) but, for a number of reasons, they do not have ability to operate below Cat 1 landing limits. Firstly, the MoD does not have an airfield equipped to operate below Cat 1 and there is considerable expense involved in achieving this qualification. Lighting/ILS have to be upgraded and the authorities have to buy/gain control of land in the runway undershoot to ensure that no external influence can be exerted on the ILS signal by passing cars or tractors etc. Secondly, the aircraft have to have their autopilots maintained to very exacting and expensive standards for continued certification to autoland. Finally, the crews need to be trained and then re-qualified every 6-months in LVOs. The MoD decided that expense involved was not worth the benefit to their operations. The logic is not unique and many airlines also choose to remain Cat 1 operators on grounds of cost.
     
  13. That'd be a career showstopper though, wouldn't it?

    "Sorry Guv, its harry-clampers. I don't care what rank you are, there's only one Captain on this airframe, so if you want to get to Paris today, you're going by surface-means"