Landing in zero visibility??

[Whoopedo_STALL]

HI :)

I assume that modern airliners now can land with zero visibility (clouds and fog) by using the autopilot etc.

But what if the autopilot stopped working? Are you pilots trained to manually land in zero visibility? Is it possible or would you just go to a different airport where the weather was better.

TIA :)

Jon.

ps. I just had a go on FS2002 at the "landing 737 blind at heathrow" flight, and crashed :(

It was very difficult!

[BlueEagle]

Landing in conditions of zero visibility requires an autoland, using the autopilots.

If the autopilot(s) fail during such an approach then a go around is required and the pilot will select an approach/airfield that is compatible with his serviceable equipment.

As aircraft often have up to three autopilots fitted and a variety of back-up systems the appropriate procedure will vary according to different aircraft/companies/the point in the approach at which the failure occurred etc.

Hope that helps.

[Thunder Child]

Correct me if I'm wrong, but I was chatting with one of our Citation Skippers the other morning re; this subject.

As it turns out, the Gulfstream V has (if fitted!) a monochrome heads-up display which can permit a pilot-controlled zero viz landing.

A taste of things to come............?

[john_tullamarine]

Thunder Child,

The ability to land 0/0 has been around for a long time.

Trident did it a long time ago .. easy as falling off a log. Most of the recent airliners can do an autoland in the same way.

Many of the HUD installations enable it to be done with ease.

With a bit of practice in the sim and reasonably good conditions, the average jock can hand fly a raw data approach in 0/0 to a full stop on or fairly near to the centreline. While you might have found MS FS a bit difficult without any of the full flight feedback cues, it is really a doddle in the sim with a bit of practice... and an excellent stick and rudder I/F scan skills exercise. I am reliably informed that, in years gone past, one of Europe's mail service's pilots routinely would fly in minima which the rest of us only marvel at ....

So why don't these latter events occur routinely in the real world ?

A lack of system redundancy, monitoring and demonstrated satisfactory risk numbers is the key to the difference between what might be able to be done and what is permitted to be done under a particular State's regulations. If the overall system's capability to land with a high level of safety (low level of risk) is not up to it, then we ought not to be doing it in a commercial environment.

In respect of routine low vis procedures (Cat 2/3A, for instance) it perhaps is not entirely as simple as BlueEagle suggests as crews need to be trained for the case where an aircraft systems failure (or wx deterioration) occurs after a point where a miss can be taken without too much risk eg. the vis goes to zero halfway through the landing roll. Clearly, the crew has to be able to complete the landing blind .. and sim exercises are structured to provide the skills and confidence to do so.

However, for the planning stage, it really is a matter of risk levels which drive the regulatory processes ..

[fireflybob]

Remember that you have to be able to taxi the aircraft to the gate after landing! I recall that this is the reason why there is a requirement for an RVR of 75 metres - from a systems point of view then, yes, you can land in 0/0 (with suitable autoland) etc. but you have to be able to see a few centreline lights to taxi in although I suppose ASMI might help you otherwise.

[dolly737]

Not only should one be able to find the gate, I find some comfort in the thought that rescue services would be able to find ME, just in case :rolleyes:

At many airports THEY determine the minimum vis required to maintain an operational status. As already mentioned above, modern autopilot/HUD systems have no problem with zero vis.

[twistedenginestarter]

Whoopedo

Here is a flavour of real low visibility landing. I don't think the Trident or any aircraft have ever done 0/0 in line service.

The Trident was crewed by three pilots, (a Captain and two Co-pilots). The
Captain sat in the left-hand seat and the P2 sat in the right hand seat and
P3 in the center seat behind the center console. P2 and P3 were equally
qualified and swapped seats leg and leg about or by the day or tour of duty
(however the wished). The aircraft was Triplex equipped (three Autopilot,
three Radio Altimeters etc.). Each of the three monitored the other two and
if one saw that it was at variance with the other two then it would switch
itself off and the appropriate warnings would be displayed on the flight
deck.
In this description of an approach, the weather is assumed to be at the
limits for Cat 3b. For the Tridents in those days, that meant a minimum
Runway Visual Range of 75 Meters at the touchdown end of the runway and no
less than 50 meters and mid point and far end of runway. The decision height
for this approach is 12 feet (Radio Height from wheels to ground). The
approach starts with Radar vectoring onto the ILS at about 2000 feet and
about 10 miles out. In these weather conditions an automatic landing is
mandatory. Any failure of a system, which precludes an Autoland, means an
overshoot from the approach and a diversion to an airfield where the weather
is suitable for a manual landing.
With the three pilot system and monitored approach of those days it was
mandatory that P2 flew the approach (controlling the Autopilot). The Captain
was not permitted to fly the approach in this weather. P3 read out all the
checklists and monitored the other two pilots to ensure that each check was
carried out. P3 was also responsible for monitoring the panels with
particular reference to the Radio Altimeters and various "Doll's Eyes" and
other indicators that denoted any triplex malfunction. He was also
responsible for the various verbal Calls that necessitated precise responses
from the Captain. With the aircraft established on the ILS localizer and
descending on the glidepath. P3 would read the Finals checklist (Gear with
one dot to go, land flap at the outer marker etc. - just like in the
simulator). P2 would be operating the various Autopilot controls (APR etc.)
and closely monitoring the main flight instruments, ensuring that the
aircraft was behaving normally and following the ILS closely. The Captain
would be monitoring his own flight instruments to verify the same thing.

At three hundred feet AGL, P3 would do a final check of various indicators
on the glare shield and assuming that all was in order he would call
"AUTOLAND TWELVE FEET". The Captain would reply "AUTOLAND TWELVE FEET". This
meant that the Autopilot would be landing and the decision height would be
12 feet. The Captain would now be peering out through the fog looking for
lights. He would have his hands on the yoke feeling the Autopilot control
movements. A bug had previously been set at 42 feet on the radio altimeters.
As the needle hit this bug, P3 would call "THIRTY ABOVE". This meant that we
were only 30 feet above the decision height. As the needle hit the permanent
bug at 12 feet on the center radio altimeter, P3 would call "DECIDE". There
must be an immediate response from the Captain to this call. He must
immediately respond with either "LAND" or "OVERSHOOT".
If the Captain called "LAND", this meant "I have control of the aircraft,
the Autopilot is going to land". P2 would slowly close the center throttle
as the Autopilot closed throttles 1 and 3. P3 would sit tight! As the wheels
touched down the Captain would press the button on the stick, which
disengaged the Autopilot and lower the nose wheels gently onto the runway.
The autorudder would remain engaged and attempting to maintain the runway
centerline by following a buried wire. As the nose wheels touched P2 would
pull up the reverse throttles on engines 1 and 3. To give full reverse
thrust. At 60 knots the Captain would call "reverse out" and P2 would cancel
reverse.
The Captain would manually brake the aircraft using the toe pedals,
disengage the autorudder at about 40 knots and if necessary use the rudder
pedals to stop the Barber's Poles streaming. If they stopped streaming left
or right, it meant you were on the centerline. In very thick fog the Captain
might have to call for radar assistance to turn off the runway and find the
taxiway centerline lights. Going back now to P3's "DECIDE" call at 12 feet.
If the Captain's response was "OVERSHOOT" or if there were NO response from
the Captain, P2 would slam all throttles fully forward. The aircraft, still
under the control of the Autopilot would rotate and climb away, without the
wheels even brushing the ground!
Finally, you may wonder just what the Captain had to see, in order to make
that "LAND" call….. Well, I'll tell you… He just had to see ONE LIGHT.

[Whoopedo_STALL]

very interesting,

Isnt the trident a really old plane? Sounds quite advanced to me!

[john_tullamarine]

.. and therein lies one of the redundancy problems with visual cues ... as any pilot who has done the exercise in the sim will attest ... it is very difficult at times to be able to identify just what light it is that he/she sees .... whether, for example, the aircraft is on the extended centreline ... or aligned with the runway side lights .. only a few feet in the overall scheme of things .. but with decidedly different roll out outcomes ......

[canberra]

are you sure a trident flew with 2 co-pilots? ive seen a trident cockpit at the museum at east fortune and it had a flight engineers station. i suggest that one of the 2 co-pilots acted as the engineer, personally id sooner have had a career fe rather than a pilot acting as the engineer.

[exeng]

To answer your question about the F/E, it depends which airline was operating the Trident. The CAA certified it to be crewed either by 3 pilots, or 2 pilots and an F/E.

B.E.A. operated it with three pilots whereas Northeast Airlines operated it with 2 pilots and an F/E. Not sure about other airlines.


Regards
Exeng

[spekesoftly]

twisted,

Thanks for the excellent description of a Trident Autoland. Do you recall which Airports were/are equipped with the buried leader cable, and was it/is it used by any other aircraft types?


P.S. Am I right in thinking that in the early days of Trident CAT III approaches, B.E.A. gave passengers on such flights a commemorative tie (broach for the ladies?) to mark the event?
Or is this just another urban myth?

[canberra]

anyone ever read neil williams story about blind landings? if you can get hold of a copy its quite an amusing little tale.

[Gerund]

Reggetably, I can't find the article but it was published in a SA flying magazine by a regular and very experienced commercial and test pilot contributor.

He was faced with that unenviable position of being low on fuel, with no suitable alternates, and having to do an instrument approach into Gander, Canada, completely fog bound, where the ground visibility was less than 100m.

In the article he gave advice on performing the unthinkable and living to tell the tale.

One thing we should always remember is that a rate of descent of 500 ft per minute is only 8.3 feet per second. The rate of acceleration due to gravity is 32.2 feet per second per second, ie after jumping off your roof, after one second you will be travelling at 32.2 feet per second. Flying straight into the ground at a rate of descent of 500 ft per minute with all that undercarriage to break and cushion the impact is unlikely to kill you, or even hurt you.

I am so sorry that I don't have the article to post, because it was full of advice on carrying out the unthinkable including advice on at what height the ILS suddenely appears to indicate a fly up which you should ignore.

He lived to write the article, and waited stationary on the runway until the Follow Me vehicle eventually found him!!

[Thunder Child]

My point earlier was referring to Pilot-Controlled 0/0 landings by use of the HUD creating a 'virtual runway' on-screen.

I'm pretty sure the Trident didn't come with a HUD as standard fit!

I'll try and dig out some articles on it and post em up.

[FJJP]

The first blind landing was done at RAE Bedford in a Vickers Varsity (I think the unit was called something like 'the Blind Landing Experimental Unit'). You may be interested to know that the Vulcan was equipped for auto-land, but it was never used. The intention to fit leader cables to military bases was never followed through - probably due to cost.

[lunkenheimer]

Do you mean 'the first automated blind landing'? I know that there were completely blind demonstration flights performed before WWII, for example by Doolittle.

[expedite_climb]

If the Captain's response was "OVERSHOOT" or if there were NO response from
the Captain, P2 would slam all throttles fully forward. The aircraft, still
under the control of the Autopilot would rotate and climb away, without the
wheels even brushing the ground!


Hmm. I know the 757 is a bit bigger than the trident but also more powerful. If we Go around from a DA of 50 ft on a cat 3a approach, we end up descending below to around 10-15 ft gear alt while the aircraft pitches up. If we have a DA of much below 50ft the gear will strike the ground during the go around - so surely this happened on a 12 ft DA in the trident ??

[BlueEagle]

I think you will find that the engines fitted to the Trident had a much, much quicker spool-up than any modern fan engine, consequently the chances of the wheels touching were less.

[john_tullamarine]

.. and, presuming that the approach has been within tolerance and that the miss is due only to visibility problems, if the wheels touch the runway .... is that a problem ?

[spekesoftly]

"Slam all throttles fully forward" ..... hmm :( ...... compressor stall? :rolleyes:

[BlueEagle]

Well, on the B747-400, doing a Cat111 in the Sim, with a DH of 20' the wheels touching during a GA was pretty normal.

[expedite_climb]

I agree its normal for the wheels to touch - infact the 75' cat3 with DA14 75m will also do just that - just surpirsed they didnt.

Trident was a bit before my time though !