Arming both ap for approach
 

Hello folks,

Regarding arming the autopilot for approach: why do we arm both autopilots for a normal cat I approach? On the 737 we always flew with the pf autopilot the ils. So is it because we could forget it?Or any technical reason?
Thanks!!

I don't know for which aircraft are you asking but on 737 if you arm both AP for approach, you get quite a bit of nose-up trim at ~ 400ft RA to help the aircraft with flare in autoland and could come as a nasty surprise as you disconnect the autopilot at Cat 1 minima in marginal weather for manual landing. I believe this is the reason why most operators choose to fly ILS approaches with only one autopilot unless conducting autoland.

For the 737 Classics anyway there was never a Boeing requirement to use both AP for a Cat 1 ILS. It was two autopilots only for an autoland which is not required for a Cat 1. Some chief pilots are very fond of publishing their own particular egos in company operations manuals. Sounds like the problem exists in your operation. :E

Because that is standard Airbus factory sop.

At least on the classic 737 fleet, flying the ILS with 2 APs will give you the chance to do a go around with autopilot. So must guys that fly ILS with the 2 APs do so to reduce workload in case of a go around, it wasn't a SOP on my previous outfit but rather a personal choice.


Cheers

It was a SOP in the airlines i have flown the 737, both the classic and the NG. Originally the reason given was to prevent an aileron hardover, a few of which happened before that SOP was introduced. But of course the easier auto-go around is another reason. And of course, the only chance for an FO to fly an autoland was during CAT I conditions, which is an approved procedure.

What could be more simpler for the average pilot than an all engines manual GA? No chance of an aileron hard-over there. After all, a one engine inoperative GA is flown manually so what's all the sweat about a two engine manual GA? You don't need a flight director for either. Unless of course one is the victim of automation addiction.

What could be simpler? Pressing one button.

Why? I mean, automatic go around is available in a one engine inoperative scenario, same as autoland to CAT IIIa standards.

And yes, of course a dual engine go around is simple enough to fly without any help, but is very rarely trained and very uncommon in normal flight operation. And then, it is not that simple anymore if the last time you did it was 10 years ago during your initial type rating...

I'm curious why Speedwinner asks the question on here and not to the in-house training dept. When the answer is given please inform us; plus was type you are on. It always help to be complete with the specific type in questions.

Sorry! A320! Have been on the 737 and now 320

not recommended in the FCTM or mentioned for a normal cat 1.

would be hesitant to do it.

views?

Again...on which type?

So the goal of my question was: why do we arm on a a320 Airbus aircraft both ap in a cat1 approach?

Pure guess here...so shoot me down....haven't looked it up....(A320 related by the way)

Could it be so that in the case of an FMGC failure (FMS), and one AP 'kicks out', that we automatically have a downgrade from CAT 3 DUAL, to CAT 1 using the remaining AP (1 or 2) and still able to continue the auto flight regime down to CAT 1 minima....

I'll get my coat lol....

F/o

What defines a "classic" 737? Seems like that would be the old clunker that had only one primitive auto-pilot. I never flew any model of the 737 but I did fly the 727. It had a lousy auto-pilot. Then, the advanced 727 came along with a slightly less lousy auto-pilot that was supposedly good for limited CAT III with a DA. It didn't auto-land. It just flared (sort of).

classic = 737-300/400/500 series.

it has an advanced autopilot capable of autoland, unlike the original series 737-100/200

BOEING 737 NG

Follow the FCOM and company policy.
 

Follow the FCOM and company policy.

In the NG it is virtually always best to use the best and full protection of the AP which is derived from using FAIL OP (with EDFCS) or dual channel FAIL PASSIVE for pre-EDFCS APs without LAND 3 capability.

The failure tolerance and protection against AP anomalies is vastly superior when using the best AP mode possible, which is achieved by using both APs.

Bottom line is follow the FCOM and company policy.

On the NG, ...EDFCS with using either LAND 3, or LAND 2 is an amazing robust system... and even the earlier dual-channel Fail Passive system was quite good.

Fairly sure I have been in a -200 (jurassic BTW...) for a Cat III autoland.

As for A320, I don't think it matters for CAT I conditions. However, if you arm both for every approach, muscle memory means you'll arm both when it counts (real CAT IIIb conditions...)

This discussion becomes rather irrelevant in more modern Boeings...:ok:

The 2 engine, manually flown missed approach is one of the most mis-flown procedures. How often do you practise one? A single engine go-around would probably come as second nature due to the number of times you encounter one in the sim.

Utilising both AP for approach frees up capacity should you have to go around two-engine. It's not about showing how awesome a pilot you are, it's about flying the procedure safely should you have to.

The 2 engine, manually flown missed approach is one of the most mis-flown procedures. How often do you practise one?

And this true comment invites the question of what the heck are we doing with one of the best training devises (sim) if there is a known problem and it's not being practiced?
Further, why is it messed up? On B737 the normal 2 engine G/A is flown as F15. If this is a manual manoeuvre it is like a F15 takeoff; the main difference is PM has to select the flaps. Other than that just press TOGA, select F15 and follow the FD. What contributes to causing a mess up is that some company's SOP's fly a G/A different from a normal takeoff. They rush to retract flaps at 400'; why? they fly it manually all the way to flaps up; why? A G/A is not a rushed affair, or should not be. It can be as relaxed as a takeoff and then it is conducted and executed correctly. If you listen to the 'mouth music' and calls of some G/A SOP's and then compare to a normal takeoff it sounds panicky, so guess what happens.
Keep it calm & simple for best results.

If everyone said

Goaround, flaps 15, check thrust

It would be a Safire place for everyone. It covers all the items to be done and to be checked.

Goaround (toga, check)
Flaps 15 (set, check)
Check thrust (set, check, adjust if required)

I can't stand the call

Goaround

Couldn't agree more with RAT 5. The simulator's ability to reset should allow the ability to knock out 10 or 12 repetitions in 20 minutes. Instead, we spend half the time trying to figure out why the sim didn't reset to the correct snapshot.

The 2 engine go-around, in real life, comes with baggage: in half the cases, your initial perception is that you yourself have screwed up...too fast, too high, not configured, etc. This is an incredibly powerful distractor to be occupying your residual attention while you're flying the most under-practiced of normal maneuvers.

In the other half of the cases, you've just been handed a can of worms...gear unsafe, no visual references in sight, etc...something that means your day just got more complicated. Another strong distractor.

Either way, you have just injected yourself into the ATC environment as a loose cannon. Lots of radio traffic at just the wrong time. First thing ATC wants to know, about the time the wheels are coming up, is what was the reason for the go-around? Seriously? How about we just fly the airplane for a bit, and discuss the paperwork later.

So this is actually a maneuver fraught with risk for a dozen reasons. The simpler the procedure, and the more we practice the muscle memory, litany, etc., the easier it will be when we need it.

The Brits were the first with auto-land circa 1968.

But, the FAA wasn't ready with its CAT III airplane requirements until the design of the L-1011 was firmed up a bit later.

It would be interesting which variant of the 737 had the first fully redundant, fail-operational auto-land system.

NG FCTM I believe does not recommend dual AP approaches for normal cat 1 approach.

Normal (baseline) FCOM Procedure is to use dual AP for ILS/GLS
 

Reference the Cat I AP use comment... Not so. The normal (baseline) B737NG FCOM Procedure is to use dual AP for ILS/GLS regardless of reported WX. See typical FCOM page that (as of 2011 and before) stated:

-Arm Approach Mode
-Engage the other AP

See NP.21.68 "Landing Procedure - ILS or GLS"

Contrary to myth, the Brits were not anywhere near being "first" with Autoland !!!!
 

WR... We ought to to talk!!! The Brits were nowhere near first to do either autoland or Cat III !!!

Col. Carl Crane was already doing autolands at Wright Field (Aug 23, 1937)
in a C-14... with Stout and Holloman...

The first ILS autoland was in '42, also at Wright field in a B247 NC-11

The Wright Field troops carried the SCS-51 over to UK and that help start what would eventually become BLEU...

Oct 1944 – B247- did autolands in a joint USAAF/RAF program
using a Minneapolis Honeywell C-1 Autopilot
and the SCS-51 ILS

On Sept 21/22 1947 an AAF C54 flew a completely automated takeoff to landing flight across the Atlantic, including an autoland, from Stephenville to Brize-Norton

12 Aug, 1957 - the Navy was doing autolands in a Douglas F-3D-1Skyknight
using the Bell Aircraft ACLS – on the “Antietam”

And the Dash 80 [B367-80] was routinely doing autolands with a jet transport configuration in '59

Further, on 29 Sept 1962 – a French Caravelle SE-210 – was doing ALs with a Lear AP (Lear 102) MC-1 AP

So yes, the British did a lot at BLEU, and contributed much, especially to the "math" now used in autoland lore, and operationally later with the "Ground Gripper", ...but they were by no means first to do either autoland or Cat III !!! See my 2015 SETP paper on this subject, relating the history of Autoland and All-Weather-Operations!!!

PS. Any B737NG with the EDFCS AP configuration is capable of doing LAND 3 Fail-Op autoland with rollout, if the airline selects that AFM and AFDS option. There are several AP and HUD configurations available, that the airline can choose.

O:)

B737: Some have claimed it is better to arm both A/P in case of a G/A then you can perform a simple manoeuvre with the push of one button. I know of some pilots who made it their own SOP, until it was reported to CP and there was a summons to a meeting. There are some airlines that have it as an SOP, perhaps.
Those against this practice say that it is OK down to a disconnect at 500'agl and then, after the nose up trim input, it gets dodgy to land. Others say that the 30lbs force for nose pushing is a shock, but Boeing have no worries.
Indeed, in B767 sim, as part of LVO training and recurrency we used to practice manual land after A/P disconnect at low level. It was easy. But then you get some airlines that demand you execute a G/A if there is A/P disconnect <400' just because of the nose up trim. Not so comfortable if on minimum fuel and the disconnect/failure means either another circuit or a diversion, which might have been unnecessary. Why don't these airlines train the manoeuvre?
If you allow arming of both, then do you also stipulate a cloud base to allow disconnect >500'? Do you then allow only 1 A/P if cloud base is below 500', but that then leads to 2 different SOP's? Do you train landing with nose up trim and allow the PF to make the decision? No way, that is far too radical.
It is quite curious how complicated this can become. B737 FCTM seem to be a little light on direct instruction. May be someone on the inside can give a definitive policy answer.

I'm surprised at this thread.

First, because I haven't experienced anyone on the 738 arming the second AP except on an autopland. Perhaps I've lived a sheltered life.

Second, and related to the above, we have had so many threads about a lack of manual handling skills that the idea of doing a dual channel approach in Cat 1 conditions as a matter of course appears to be evidence of a huge lack of confidence in manual flying skills.

Or a particular airlines SOP to require it. You can never know...

Answer to the FCTM question ref advice for AP Arming
 

At least as of the July 29, 2011 version of the FCTM, ...for which the advice likely remains the same and goes back at least to the initial availability of the EDFCS AP option,...

See FCTM "Approach and Missed Approach" Page 5.14 (-300 to-500 Fail Passive), 5.15 (-600 to -900 Fail Passive) , and 5.16 (-600 to -900 Fail Operational).

In all three cases the advice is:

-ILS or GLS tuned and identified
-LOC and GS Pointers shown
-Arm APP
-Second AP CMD

Never a truer word. Proof of the pudding when you read Loss of Control In-Flight is now the major cause of airline fatal accidents

I would argue that both things do not necessarily have anything to do with each other.

I fly in an airline that both actively promotes manual, non FD flight as much as possible and still has the dual AP use in all cases SOP.

If someone wants to fly a raw data approach out of FL390, not a problem, go right ahead. If one however, for whatever reasons, elects to use the auto flight system, use two autopilots for approach, even if you plan to switch them off later on anyway. It gives the option to continue using the automatics until the end of the rollout or go around.

7478ti:

What was the target level of safety on those early auto-land systems? Were they fail operational?

BTW, I am curious which 737 type was the first 737 to come with two autopilots, and with the equivalent level of safety and operational capability as the early 767s?

EDIT: Several years after TWA completed delivery of its 727-231s they placed a follow-on order for ten "advanced" 727s (727-231A). It had a souped up version of the same crummy auto-pilot as the earlier 727s. But, it could do what they jokingly called CAT III (50' DA, 1,000 RVR). It would flare, but not decrab nor did it have rollout guidance. The pilot group basically boycotted that feature.

Answers to aterpster (WR)
 

Q1:What was the target level of safety on those early auto-land systems? Were they fail operational?

A1:They all met AC20-57 or equivalent, as well as AC120-28 (as amended, depending on the year certified)... Some were Fail-Op, and Some were Fail-Passive. TLS was a fuzzy contrived (non-FAA) math concept in serious disrepute, for some very valid fundamental conceptual reasons at the time (and in fact still is in disrepute even now!, ...versus using FHAs, FMEAs, and SSAs, to meet the criteria of AC120-28D). Note: the B747 was the first WB jet to have a purpose designed Fail-Op AL to actually be certified (It was a triple channel SPZ-1 bought by a few European airlines - Note: most early US airlines bought the B747 with the dual channel SPZ-1 which only had FP AL) but all early B747 versions still did not have rollout capability, until the "rollout special conditions was signed", and then the rollout feature was added. However the L1011 had a very good Fail-Op AL system (FCS-110) and it preceded the B747 for Cat III Op-Spec approvals. The DC10 system (PB-100), while nominally having an AFM airworthiness approval for "Cat III" back to the early days similar to the L1011, didn't get operationally cleared for Cat III until many years later (~1977 as I recall), when we did the first approvals on AA's DC10s, with the upgraded -30 gains and revised AP boxes. The DC10 AL system wasn't nearly as good of a system as the L1011s AL, or even the B747s. But it wasn't until the B744 that the B747 finally fully caught up to the L1011 for having a reliable Fail-Op AL capability with a significant usable flight envelope, in terms of both robust atmospheric tolerance, and ability to cope with irregular terrain. The A300 AL also had problems along the way, and those issues remained for much of its service life, but it eventually did get cleared (albeit with restrictions) for both Cat IIIa, and later Cat IIIb.

Q2: BTW, I am curious which 737 type was the first 737 to come with two autopilots, and with the equivalent level of safety and operational capability as the early 767s?

A2: The early B737s were optionally provisioned for dual channel FP AL to TD, with both the SP77 and later the SP177. But it wasn't until the control laws and other functions were upgraded in the Classic (B737-300/400/500) to achieve roughly the same basic FP AL (safety and operability) capability to TD as the early B757/B767 LAND2 mode that it could in any way be considered as equivalent. (Note: Even then, the B737 Classic was still NOT Fail-Op at that point, and still did NOT have rollout capability). The B737 didn't actually get a rudder channel, alignment, rollout, and LAND 3 Fail Op capability, until mid-way through the NG series, with the introduction of the new R/C EDFCS AP. Now the B737NG EDFCS AP is a terrific AP, fully capable of reliable Fail-Op, even in horrendous winds and gusts, and irregular terrain, either all engine, or OEI.

Q3: Several years after TWA completed delivery of its 727-231s they placed a follow-on order for ten "advanced" 727s (727-231A). It had a souped up version of the same crummy auto-pilot as the earlier 727s. But, it could do what they jokingly called CAT III (50' DA, 1,000 RVR). It would flare, but not decrab nor did it have rollout guidance. The pilot group basically boycotted that feature.

A3: That B727 version was the dual Channel FP SP-50 Mod Block 4 AP, and SP150 AP. You're correct, in that it didn't have the alignment and rollout capability of the later APs. But it was nonetheless approved for, and safely and successfully flew Cat III FP, with both EAL and DAL (to a 50' HAT DH and eventually RVR700/700/700), and with other airlines too. [Historical note: I was on the very first B727 FP AL Cat III "proof of concept" flight back in the early 70s, ...as we flew multiple approaches to KOKC in N27 (which was specially modified with the recently upgraded AP, in actual Cat III fog, ...with Boeing's Mis Sekajima introducing various pitch and roll hardover and slowover faults into the AP, even during flare (and unknown to the subject pilot during the event), ...as "proof of concept" testing]. It is also noteworthy, that in it's Cat III ops history, the B727 AP certainly wasn't as good as later APs, but in its entire operating experience during that period, there were no reported significant safety events in low visibility conditions related to the AP or AL use per se. However, there were HF related events that occurred, but they typically were due to crews disconnecting the AP, and trying to hand fly to a landing with very marginal visual reference (e.g., the KORD event). I'm well aware of the TWA B727 FP AL controversy, and Larry DeCelles views, as well as Joe Oliver at DAL, and the many others who were advocating for taking various courses of action back in those exciting days! What memories!

Thanks for the great answer, TI.

As to TWA's advanced 727, it wasn't just the "trouble makers." Most of the line pilots did not like the "J C Penney's" auto-pilot. Some tried to stick with it, but eventually threw in the towel. The group was often biased by prior experience as L-1011 F/Os.

Well Stated aterpster, ref the B727 SP50/150
 

I concur... but note...

All we had back then was essentially the Caravelle Lear MC1, the Trident complete kluge of a mess, and the B707 PALS and PB-20, the HUD on Col. Klopstein's N262 trying to get it on the Mercure, with the promise of finally doing it right with the B747 SPZ-1, either dual channel or triple channel, albeit still with no rollout capability. From that foundation, Lockheed (and Douglas) finally both did a design that was much better (Fail-Op as well as reversionary Fail-Passive), that led to the great system on the 1011, ...and great "attempt" on the DC10, but nonetheless fouled up execution on the PB-100 on the DC-10 (until it was fixed much later after partial resolution of the UAL/Douglas "who pays" fight).

So the B727 at the time looked pretty good in comparison!!!

This was all while the DC9's with their pre-906 AFDS, and the B737's Jurrasic APs never did get much traction, and never got much farther than somewhat useful Cat II.

Even the C141 (AWLS) and C5 were all fouled up at the time with AWO issues, which partially led to the Specked Trout AL and AWO effort, and the ILM on AF 624133 (both "my" jets in that era), and the massive Pi-Fax T39 effort at IPIS/IFC, and the Mythical Landing System (MLS) in parallel.

And even as late as the 80s, the A300's were still all fouled up for AL (many reasons,.. from delta-psi preset course error sensitivity, to stby AI reference drift, to pitch thrust coupling, and nearly complete inability to tolerate irregular terrain). So by Dec 1, 1977 (signing of AC120-28B), and opening up of the 30+ AN/GRN-27 ILSs, as Type II ILSs, to support Cat III 50'DA(H) RVR700 ops,... it looked like a much better and safer thing to do to use the B727's AL capability than continue with the countless low-vis (manually flown) accidents we were having, starting with Williamsport in '59, that led Ed Burke (AAA) to try to take action at the "All-WX-Flying Committee", ...long before even the DeCelles/Oliver era.

So while the B727 did have "non-optimum" AP/AL aspects, it was ultimately successful and safe, and finally help break through the many operational barriers to doing Cat III, ...since it was "good enough", and it used so many more destinations than the L1011 where Cat III minima could be applied. In the end, it was as least as important to ultimately making Cat III practical globally, than the L1011, and much more so than any European jet or set of airports.

B Regards!!!

I thought that the HS Trident had one of the earliest operational autoland systems. ?

Trident had AL, but it wasn't either the first or the best at the time
 

Yes, Trident did have AL, but it wasn't either the first AL, the first jet AL, or the first jet transport AL, or anything close to the best AL system at the time...

The Trident did however, achieve some "firsts", as noted below:

The Trident was the first “air carrier” automatic landing with passengers on board, on 10 Jun 1965 – British European Airways (BEA) HS-121 Trident 1C flying as BE343 LFPB-EGLL - with a Smiths SEP-5 AP – ...but it did it with significant regulatory restrictions. The specifics were: a commercial flight with passengers aboard, achieved on flight BE 343, with a Trident 1 G-ARPR, from Paris Le Bourget to Heathrow Rwy 28R, with Captains Eric Poole and Frank Ormonroyd

Then, in Nov 1966 - BEA HS-121 Trident - made the First air carrier (non-revenue) civil AL in fog - at London (EGLL) Rwy 28.

And finally, on May 16, 1967, the Trident made the first 3 Ch A/L with Passengers - that was Trident 1C G-ARPP – Nice/London

Nonetheless, the Trident and its Smiths AP did make valuable contributions to the AWO and Cat III evolution, and state of the art...