With particular reference to London Heathrow in the fog they had on Monday 2nd and scheduled airline operations.
Why does fog cause such disruptions to scheduled flights when CAT IIIB and I assume GPS landing systems are available?
I know that too much ‘metal’ (aircraft) on the ground distorting the CAT IIIB ‘beams’ is a problem and guess approach separations during these operations are greater and holding points are further away than on normal operations.
Is it the ground taxing in fog that slows the whole operation down? and since the airport, even in good weather conditions, is working at maximum capacity then fog just causes holdups / cancellations.
Where does LPV (GPS) approaches come to the rescue in all this?
Are LPV (localizer with precision vertical) approaches in full operation at the likes of EGLL and can all the major airlines make use of it?
I also guess that long haul flights are in the air and priority has to be given to getting them ‘in’ before the departure of new flights.
This question was put to me by my aviation orientated grand nephew and I found I could not really give a definitive answer except that ‘fog is fog’ and one just expects delays !!
I should think planes are separated by more time/distance in poor visibility?
Yes, Munich has CAT IIIb as well and automatic landings, but they need more seperation in dense fog and taxiing is slower too.
Is every plane operating out of Heathrow CAT3?
What about the twin turboprops?
That’s a point Peter. Guess some flights could get ‘out’ but conditions, lack of CAT3 etc, means they can’t get ‘in’ at their destination, so they get delayed / cancelled.
My grand nephew thinks that modern system and computers should be able to eradicate the effect of fog – if only it was that simple.
During LVP, the runway protected areas are bigger/larger in order to prevent localizer signal disruption.
The large runway protected areas needs to be free when an aircraft reaches 2 nm on final.
In order to achieve this, we need to increase aircraft spacing from about 80s to 180s. It divides our hourly rate by 2, so it creates a lot of delay.
Turboprops like ATR’s are CATII approved at my airport.
But sometimes, some modern jets (Boeing 737 NG / A320’s) have to divert because they are unable to perform CATII/CATIII. I guess that’s because the crew is not “CAT III current”.
Airports operating at maximum capacity combined with fog induced hourly capacity reduction by 50% sums it up.
Peter wrote:
twin turboprops?
I think most turboprops and light jets / business jets are CAT I/II. Aircraft certification / crew training is a cost/hastle factor.
The Dash 8 / Bombardier Q 300/400 and CRJ series can be certified for CAT IIIA (HGS – heads up guidance system). Some airlines splurge the couple hundred thousand Euro per airframe as it impacts dispatch reliability for Eurocontrol slots (or something in that order).
There was an interesting article in flying about an arrival into heathrow. The author a commercial pilot for a major american airline who writes a regular article was relating that their sops require the crew to be current with an actual cat 3 landing, not just in the sim, within the last (i think) 12 months. He wasnt and said he would have had to divert even though the aircraft was capable and all systems operational. I understand that ba in contrast has no equivalent sop.
We have to fly a CAT II/III every 6 months (between recurrent sims.) Based in NW Europe on shorthaul it’s not a problem quite frankly to fly a live one within that timeframe.
There are various minor dispatchable faults that leave a certifiable CAT III aircraft downgraded to CAT I only until they are fixed which may be why they divert. Some airlines are better than others in both repairing these deferred defects and making sure you have a CAT III aircraft if fog is forecast.
There are also different levels of CAT III operations. CAT IIIa has a DH of 50 ft and RVR required 200m which at some points this week has not been enough for many London airports. Cat IIIb requires extra equipment on the aircraft and can have no DH with a min RVR of 75m which may also explain Guillaume’s diversions.
We revalidate in the sim. Don’t get enough landings to give any away to the autopilot.
It was properly foggy at Heathrow on Monday. LVP take-off 27L. Only the second or third one I’ve flown in 27 years in the airlines!
