View Full Version : CAT III App

21st Feb 2004, 07:23
Its kind off a silly question, but I've heard a CO from a portuguese company stating that he turns off all lights on the a/c, except beacon, when on a CAT-III approach...:confused:
Seems to me a very odd procedure :uhoh: Does this makes any sense to you?

21st Feb 2004, 10:43
It makes a lot of sense and its not odd at all really.

Having landing lights on when the vis is really bad just makes it harder to see the touchdown zone lights. With decision hts of 20 feet or so you dont need the landing lights on, all they do is reflect off the fog causing you problems.:D

21st Feb 2004, 22:39
Very normal for a lot of airlines/people to do this. Altouhgh I've never seen people turn off their nav lights.

Ever fly in fog with the strobes and LL (landing lights) on? With the reflections, the strobes can actually be redirected into the flight deck which can temporarly freak the pilot as he/she's reading his/her instruments during a seriouse time, the LLs can also create glare problems. This also may bother other aircrafts in the vincinty as it is hard anyways to figure out what directions the light is coming from and may confuse them. I've seen pilots perform CAT2 approaches (I know we're talking about 3's..) and even the strobes from them light up the entire airport with the fog and you can't tell what direction it's comings from...
Again this is usually with strobes and LL's, I'd never turn off the Nav's, turning off your nav would mean your aircraft would be invisible every couple of split seconds as the beacon only flashes every split second and usually nav's are not as bright as strobes or landing lights. :ok:

22nd Feb 2004, 01:07
UK research at BLEU in the late 70’s supported the theory of not using landing lights during Cat 3 landings. Some test with lights set downwards suggested some improvement but the best results for pilot vision / awareness was achieved by adjusting the approach and runway light intensity.

In general, whilst high approach and runway light intensities could give the earliest point of contact, the very high levels of glare made height and position more difficult to assess, particularly if a manual landing was authorised in the event of autopilot failure. Thus whilst a medium approach light setting often gave the best results, the overriding factor was the variability of the fog conditions – layers, thickness / density, etc, thus the policy was to leave the lights set to high intensity. This policy followed the CAA desire to focus on auto land for Cat 3 and the reduction of manual (head down) Cat 2 approaches. (Not allowed now?)

Adjusting the runway light intensity did give beneficial results. The edge lights could be at higher intensities, but the touchdown and centreline lights should be set to low intensity. These settings gave the best results at night. In daytime fog, the light intensity made little difference, except for the first point of contact, which improved at high intensities, but this was mainly true for coloured approach lights. Some tests used reduced lighting patterns; this data has been in the minimum approach light requirements. At least one daytime landing, auto approach – manual touchdown, was completed without any approach or runway lights at all - from a 50 ft DH.

Use of landing lights? The options to turn them off was given to the operators, but most were reluctant to switch them off just in case they missed the approach and suffer commercial consequences, but actually landing lights-off operations make the crew’s judgment task much easier. I suspect that this is even truer with the higher intensity lights used today. Approach strobes are good for Cat 1 + visibilities but are disturbing in low vis; aircraft strobes should be off in fog.

22nd Feb 2004, 03:12
I understand that strobes can be annoying in fog :eek: , and LL's do cause glare problems :uhoh: , but IMHO killing the NAV's its a bit too much, as sanket_patel also stated.

From what safetypee said, and I agree, seems to me that the App lighting should get more attention on those met conditions.

I would like to tank you all for the input :ok:

Best Regards

22nd Feb 2004, 07:10
must admit here I didnt think that you meant that he also turned of the nav lights as well, just thought you were talking of landing lights and strobes.

reminds me of my old exam days ie rtfq !! cya:D