TV program just watching. Two rather startling statements about fog and aircraft.

1) Search and rescue helicopters can’t land in fog. Really, if it can’t land in fog, what use is it? Hasn’t anybody invented radar?

2) A fog at Heathrow resulted in the cancellation of 180 flights. Not because it stops aircraft from landing, but because the air traffic controllers can’t see the planes on the ground. That’s a little problem, that could be very easily fixed with differential GPS.

Not sure why not, but I do recall in Canberra it was a reckless act in winter to book an early flight, fogs made for delays, better to book a bit later.

Whether or not a helicopter can land in fog is a highly variable thing.

It depends on the helicopter , the pilot and his/her experience level, where the landing is to be, just what level of fog there is, and whether or not you have someone on the ground equipped and trained to do a ‘talk down’ to nearly ground contact.

These days, there’s equipment like Skylens, smart goggles that arefed by multispectral sensors on the helicopter nose, allowing the pilot to see through just about any conditions. If your budget runs to something like that, your problems are much reduced.

I know of US Army helicopter pilots who were trained in instrument-only flying. Their side of the cockpit blanked off, no outside vision at all. Instructor in the left seat, normal external vision.

As one of them said, ‘i’ve flown all over the south-east of the US, and landed at and taken off from more airports and airfields than i’ve ever seen with my eyes’.

mollwollfumble said:

TV program just watching. Two rather startling statements about fog and aircraft.

1) Search and rescue helicopters can’t land in fog. Really, if it can’t land in fog, what use is it? Hasn’t anybody invented radar?

2) A fog at Heathrow resulted in the cancellation of 180 flights. Not because it stops aircraft from landing, but because the air traffic controllers can’t see the planes on the ground. That’s a little problem, that could be very easily fixed with differential GPS.

The only aircraft that I know of that can land in heavy fog are ones certified for a Cat 3C Instrument Landing System* (ILS), and the airport also has to have the gear on the ground to do that. I don’t know a lot about the navigation quirks of choppers, but I doubt any on them would have the gear for anything more than a Cat 1 approach.
Radar isn’t much good for close-in stuff like that, it just hasn’t got the find detail needed to accurately (better than a few metres) position the aircraft in 3D space above the landing area.
FWIW the Airbus A380 has a moving map system so you can see where the plane is on the airport, no matter what the visibility is.

The control tower problem is world-wide. It’s often because to be able to see the far ends of the airport, the tower control room needs to be fairly high. When the cloud base is low enough to require an ILS, the tower can be covered in cloud so not much can be seen. What is normally done is when you get off the runway, you call the ground frequency and tell them you’re clear. The aircraft have a radar transponder that does give a fairly accurate position, but usually any speeds less than about 60 – 70 kts are blanked out in software, to avoid things like reflections from trucks driving down the highway, etc.

• Cat 1 is a cloud base of 200’, a vis of 550 metres. Cat 2 is 100’ and 350 m vis. Cat 3A is 100’, vis 200 m. Cat 3B is 50’, vis 50 m. Cat 3C is zero-zero. Cat 2 and above requires the aircraft to be able to do a full auto-land, with no pilot intervention – And that includes tracking down the centreline of the runway after landing. The really tricky bit is getting off the runway, as you can’t really see where you’re going.
  ILS catagories

mollwollfumble said:

TV program just watching. Two rather startling statements about fog and aircraft.

1) Search and rescue helicopters can’t land in fog. Really, if it can’t land in fog, what use is it? Hasn’t anybody invented radar?

dunno but maybe they want to see where their rotors and tail rotor are so would need something like 270×360 resolution. then where do you mount it? on top or underneath? or have more than one?

FWIW, this is what you see with a –

Cat 1
Cat 2
Cat 3A ?
Cat 3B
Cat 3C

The worst ever air disaster occurred on land in the mid 1970s when two passenger 747s collided on the runway in fog. Neither plane could see each other due to fog, and ATC could see neither and were relying on radio to co-ordinate operations. The crew of one plane misunderstood the instructions and started take-off run before the other had cleared the runway.

I guess that incident put a blanket ban on fog operations. There might be technology available now like GPS that could provide a solution.

party_pants said:

The worst ever air disaster occurred on land in the mid 1970s when two passenger 747s collided on the runway in fog. Neither plane could see each other due to fog, and ATC could see neither and were relying on radio to co-ordinate operations. The crew of one plane misunderstood the instructions and started take-off run before the other had cleared the runway.

I guess that incident put a blanket ban on fog operations. There might be technology available now like GPS that could provide a solution.

It’s funny, even after the disappearance of MH370, it is still not the case that planes have always-on GPS trackers that cannot be turned off by crew.

dv said:

party_pants said:

The worst ever air disaster occurred on land in the mid 1970s when two passenger 747s collided on the runway in fog. Neither plane could see each other due to fog, and ATC could see neither and were relying on radio to co-ordinate operations. The crew of one plane misunderstood the instructions and started take-off run before the other had cleared the runway.

I guess that incident put a blanket ban on fog operations. There might be technology available now like GPS that could provide a solution.

It’s funny, even after the disappearance of MH370, it is still not the case that planes have always-on GPS trackers that cannot be turned off by crew.

Yes. It could solve both problems.

dv said:

party_pants said:

The worst ever air disaster occurred on land in the mid 1970s when two passenger 747s collided on the runway in fog. Neither plane could see each other due to fog, and ATC could see neither and were relying on radio to co-ordinate operations. The crew of one plane misunderstood the instructions and started take-off run before the other had cleared the runway.

I guess that incident put a blanket ban on fog operations. There might be technology available now like GPS that could provide a solution.

It’s funny, even after the disappearance of MH370, it is still not the case that planes have always-on GPS trackers that cannot be turned off by crew.

Such a system would also need a data-link to home base, etc. Either by satellite and/or HF radio.

A lot of this likely comes down to money. Systems exist, or could readily be developed, to allow instrument only flying in pretty much any aircraft in pretty much any conditions, but are cost prohibitive. By the same token, to choose just one example, we also have the means to develop any technology we need to colonise Mars, but no one’s willing to pay for it (except Jeff Bezos, so that’ll be interesting).

Spiny Norman said:

dv said:

party_pants said:

The worst ever air disaster occurred on land in the mid 1970s when two passenger 747s collided on the runway in fog. Neither plane could see each other due to fog, and ATC could see neither and were relying on radio to co-ordinate operations. The crew of one plane misunderstood the instructions and started take-off run before the other had cleared the runway.

I guess that incident put a blanket ban on fog operations. There might be technology available now like GPS that could provide a solution.

It’s funny, even after the disappearance of MH370, it is still not the case that planes have always-on GPS trackers that cannot be turned off by crew.

Such a system would also need a data-link to home base, etc. Either by satellite and/or HF radio.

Agree. Differential GPS has better than 1 cm accuracy, so is good for on-ground at airports.

Plain GPS has an accuracy more like 20 metres horizontally and 50 to 100 metres vertically, so (fingers crossed) is good for flight.

Kothos said:

A lot of this likely comes down to money. Systems exist, or could readily be developed, to allow instrument only flying in pretty much any aircraft in pretty much any conditions, but are cost prohibitive. By the same token, to choose just one example, we also have the means to develop any technology we need to colonise Mars, but no one’s willing to pay for it (except Jeff Bezos, so that’ll be interesting).

Not cost prohibitive. Doesn’t cost significantly more than $100 a set. Can take some time to initialise.

$100? Seriously? But at that price then OP is right – they should be on every drone, let alone every aircraft.

Can’t even drive cars properly with GPS only, let alone fly a plane.