View Full Version : B737 Fail Operational

31st Oct 2008, 04:55
Anyone knows if and eventually how many B737 NG around the world are Fail Operationel (Cat IIIB and single engine autoland)? Manuals says it's an option, another "non official source" says that presently there are no 737 fail operational, hence my questions.


31st Oct 2008, 07:49
I thought cat iii meant 3 autopilots hence why the 737 hasn't made it so. We only had 2 autopilots on the 747-200 and the were cat 2. It may be possible that the HUD will allow flight to cat iii as the 3rd indication system but the HUD receives its data from a different source and can conflict with an auto land. Good question and look forward to someone with more knowledge answering it for you

stator vane
31st Oct 2008, 08:19
73's have been cat 3A for years with two A/P's. then there is cat 3B and cat 3C. different minima.

i suppose the real factor is MONEY-and cost versus return.

the flight crew training manual for the 73 does indeed mention fail operational, but it also mentions HUD's and other bits and bobs that one must purchase to put on board along with authorizations that require money and training.

31st Oct 2008, 08:46
All NGs delivered since Feb 2003 (l/n 1278) have the Collins EDFCS which has provision for a rudder channel. Not all operators have it enabled. See here (http://www.b737.org.uk/glareshield.htm) for more info.

31st Oct 2008, 10:17
We have 85 more 737 (mixed 700 and 800) on order currently, the first three of that lot are delivered (should be 6 by now, but the Boeing strike...) and they are most certainly CAT IIIb approved. Works like a charm to be honest, much smoother approach and perfect rollout, even with close to the limit crosswind.

Don't know if the following stuff is new, it is certainly for me as we switched from -300s to 8 year old -700s and now brand new ones. Added to CAT IIIb they all allow IAN approaches which makes non precision approaches a non issue as you fly them with exactly the same procedures as you do fly an ILS. GLS (or GBAS) capability is another feature, but since airports with working GLS approaches are so rare i didn't have a chance to try it in the real world yet. The vertical situation display is a gimmick and quite usefull in mountainous terrain, but it is to be used situational at best (need bigger screens for that).

31st Oct 2008, 14:24
Same situation as Denti describes in my company, but we do have a GLS approach (at Bremen EDDW). Nice and easy to fly.

SE Autoland approvement is on our planes, but we as a crew need also to be certified and as we do not get any simulators for this procedure we are currently not allowed to fly that, despite the plane is capable to do so.

1st Nov 2008, 00:12
Denti – 737 CatIIIb?
How is this achieved with two fail passive autopilots, or is the aircraft fitted with HUD enabling a ‘hybrid’ operation?
Is it possible that the aircraft certification (CS AWO) is for CatIIIa using a 50 ft DH, but the operational approval (EASA Ops 1 – JAR OPS 1) enables a non standard – extended operation in RVRs less than normally accepted for CatIIIa?

EASA/CS AWO. (www.easa.eu.int/ws_prod/g/doc/Agency_Mesures/Certification_Spec/decision_ED_2003_06_RM.pdf)

EU OPS 1 (http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2008:254:0001:0238:EN:PDF), see subpart E. http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2008:254:0001:0238:EN:PDF

1st Nov 2008, 00:26
The 737 actually has two fail operational autopilots (if you pay for it) and that of course enables CAT IIIb operation, same as for the small buses. You can of course order additionally a Head Up Guidance System but that is not a requirement, just another option and does not enable CAT IIIb on its own.

It is certified fully CAT IIIb for no DH and 75m RVR, our crews are getting the training currently (1 hour simulator practice) to be certified as well, until all crews are certified the operation is of course still limited to normal CAT IIIa rules, after that we can do as said above no DH/75m RVR on LAND3 and 50ft 125m on LAND 2 (special performance certification for LAND 2).

1st Jan 2016, 04:17
We currently have around 26 B737s operating CAT3B in India all are fail operational. However as you correctly pointed out there is no supporting material for operations in CAT3B from Boeing.

5th Jan 2016, 00:19
All of the 738's delivered to Virgin Australia over the last 3-4 years are Fail Operational.

5th Jan 2016, 13:41
Denti: no DH/75m RVR on LAND3 and 50ft 125m on LAND 2 (special performance certification for LAND 2).

Please advise; when is Land 3/Land 2 displayed? in my B767 days it was 500'. Is there a rudder roll out channel? I assume so.
Do you have Cat 1 reversal? i.e. can you also have 'No Autoland' displayed? What do you do then? Revert to CAT 1 DA or G/A? When & how do you 1st check that autoland might be possible, i.e. confirm 2nd autopilot has engaged in CMD. This happens by 1200' after ILS integrity check.

5th Jan 2016, 14:03
LAND2/3 is displayed after the autopilot confidence check when the second autopilot engages. Around 1200ft AGL. Yup, a rudder channel is required as CAT IIIb requires automatic rollout (yes, a HUGS would be ok as well, we don't have that).

Yup, there is CAT I reversal with a NO AUTOLAND message, if above the minimum simply switch the minimum selector to BARO and continue to the CAT I minimum. We usually (not SOP, but suggested technique) set the CAT I minimum on the BARO scale, then switch it over to RADIO and dial it down to nothing. That way we still get a triangle at the CAT I minimum, which is usually at 200ft AGL where the land/go around decision has to be done as it is the alert height. If below the minimum it is a mandatory go around of course. Personally i would rather go around if something like that happens below 1000ft AGL and sort it out afterwards.

Press the additional cancel/recall button on the MFD panel above the upper DU which displays any autoflight failure messages on the upper DU. It is installed below the SYS button. Has to be checked whenever a checklist calls for a recall check. Usually additionally pressed during the approach briefing to make sure that the required mode is available.