I recently flew out of Atlanta Int'l to Salt Lake City last week on a 767-300 and after getting airborne over Atlanta, I noticed that the flaps were not retracting and that the aircraft was remaining level and at the below the flap maximum speeds. We remained at what I thought was 5 degrees flap setting for about 15 minutes and then the Captain told us that they had a slight problem with retracting the flaps and that he was in contact with ground ops at the Atlanta airport which is the major hub for Delta airlines. They told him that it was up to him whether or not he wished to come back to Atlanta and land or to proceed to Salt Lake City, Utah. The Captain said that since they had to execute a landing anyway, he elected to proceed to SLC. He went on to say that they lost the Primary Hydraulics and that they were retracting the flaps using the Electric back-up which was quite a bit slower in the rate of retraction. We did land successfully in SLC and I later asked the Captain what happened and he told me that he had a flap disagree and could only lower the flaps to 20 degrees and that our Vref was increased to 162 kts instead of the lower Vref's at the required 30 deg flap setting. I was wondering if this is modeled in PS1.3a. I tried the Flap malfunction scenerio and got a Flaps Primary annunciaton on the Eicas. The abnormal list on page 307 is quite vague as to what actually is occuring since it only says to plan for add'l time for flap operation and to monitor the secondary flap extend airspeed of 160 KIAS from 25 to 30 degrees. Since this happened on take-off, what exactly did occur and what brought up the flaps. I assume it was the electric demand back-up pumps but I'm not sure. Also, what system did he use to extend the flaps? I assume it was also electric and he could only get them to 20 degrees since one of the problems was only one side could go down to 20 so he could only extend the other one to 20 also to avoid an asymetrical configuration. Is there anyone who has had a similar event happen and also, where can I read more on this subject since I actually experienced the real event. I assume they practice these types of malfunctions in the simulator training that they have to do, but I'm curious as to what really happened in regards to the hydraulics vs. electrical back-up systems for the flaps. Also, on page 307, I noticed the Flaps Control and Flaps Drive annunciations....What exactly are these malfunctions and how would you get the flaps down if you had a flaps drive problem where it says to not use alternate flaps??? Use VREF25 ???? I'm really confused now..When exactly do you use the Flap Altn switch etc.? Sorry for the long listing of events. Any help would be most welcomed. Regards to all,

G'day, Jack.Although I haven't been trained on the 767, I have some good books at my disposal ;-)The flaps are driven by power drive units, rotating drives, angle gearboxes and screwjacks (amongst other things). The Flap power drive units (PDU's) on Boeings have two motors: An electrical motor and a hydraulic motor. The inboard and outboard trailing edge flaps on a 767 are powered by a single PDU (unlike the 747-400, which has 2 PDU's, which allow the inboard and outboard flaps to run independently under certain circumstances).On a 767, the flap lever normally sends a position command "signal" to the PDU via (mechanical) steel cables (The 747-400 flap lever sends electrical signals to 3 Flap Contol Units(Computers), one of which will send an electrical signal, during normal hydraulic operation, to a "Flap Input Actuator" (small servomotor) which then operates a mechanical linkage which then simultaneously controls the two PDU's which will then drive the I/B & O/B flaps).On the 767, the cables run all the way from the cockpit flap lever to the right hand wheel well where the PDU is located. The 767 also has a (single) computer monitoring the operation of the flaps. This is known as the "FSEU" (Flap/Slat Electronics Unit). The computer is there to stop the flaps operating if, say, an asymmetry has been detected or to command the flaps to retract a notch if you are flying too fast (I don't think this is modelled in PIC however(?)).If (Center) hydraulics are not available on a 767 or the hydraulic motor in the PDU has failed, the flight crew must manually select the electric mode of operation via the switch(es) on the F/O's instrument panel (This is slightly different from the 744, which will automatically switch to electric power (Primary Electric Mode) if the flaps will not drive hydraulically. However, if the 744's (3) Flap Control Units(computers) fail to operate the flaps in either Primary Hydraulic or Primary Electric mode, it will be necessary to manually select the Alternate Electric System. This uses the same electric drive motor in the PDU's, but, electrical signals from the cockpit completely bypass Flap Control Units).During electrical ops, the hydraulic motor is depowered, to prevent the electrical and hydraulic systems fighting each other. BTW, the electric motors are somewhat less powerful than the hydraulic motors, so the gearing has to be lower.... hence the slow ops: Electric ops is 6 times slower than Hydraulic ops). The electric motors are also susceptible to overheat, so you shouldn't cycle the flaps up and down without allowing for a proper cooldown period. Engineers are taught that for every four minutes of electric ops, we should let the flap motor cool down for 15 minutes. Whether the pilots are governed by these rules, I can't say (I can imagine that when the gear is up, the heat from the wheels/brakes will not be assisting at all with the cooling of the flap drive unit. On the other hand, with the gear down, there will be a lot of fresh, cool air in the wheel well).I'm not really sure what was happening on your particular aircraft. The Ground Engineers would, however, make use of all the tools available to them: The FSEU has a fault recording system, so, the engineers, apart from carrying out visual inspections of the flaps for obvious signs of damage, would interrogate the FSEU for faults. The PDU has a position sensor and "Flap Disagree" messages are generated when the PDU has not reached the commanded position within a certain time frame. This message is inhibited however for things like Flap Asymmetry, during Load Relief, if there are dead position sensors, etc.I'm sure the pilots are well-trained for situations like this. They will, I suspect, have manuals, tables and the like to tell them what to do, what speeds to land at, etc. (As you may have noticed, the 767 PIC FMC has a handy Vref setting for Flaps 20 landings).Hope this helps.Cheers.Ian.

From a pilots point of view...The most likely thing was that as they tried to retract the flaps they recieved a "disagree" message, meaning the flaps were not moving as commanded (whether this was caused by a failure of the flap/slat system, or the centre hydraulic system I'm not sure).The non-normal checklist states that you arm the alternate system for the flaps or slats as required, and position them using the alternate flaps selector. A limitation of the alternate flap system is that it cannot go past flaps 20, so a flaps 20 landing must be made. The alternate system is electric (and has nothing to do with the electric demand pumps of the centre hydraulic system), and thus requires the extra time to extend or retract the flaps.In this case I'd say the alternate system worked as it should, and they were able to retract the flaps and continue on as normal.If the problem were a flap "assymetry" then you must NOT under any circumstances attempt to move the flaps at all. You must simply land with whatever you have at the time. This is a reflection of the danger associated with having an assymetrical flap configuration (ie it would roll you uncontrollably).Be very careful trying to compare the 767 and 744, as the systems are very different in some ways!Ian, as a pilot we have no information regarding overheating of the alternate flap motor.

Thank you Ian and HPSOV for the definitive explanations. I was hoping to hear from at least Ian or HPSOV and what a pleasant surprise to hear from both of you.Once again, thanks for the explanations and regards to both of you.Jack

> A limitation of the >alternate flap system is that it cannot go past flaps 20, so >a flaps 20 landing must be made.Is this more of an operational/aerodynamic thing rather than a system logic limitation, HP? I can't seem to find anything in my notes telling me that that TE Flaps 25 or 30 can't be selected in Alternate Electric mode (Perhaps it's because we (engineers) don't have to worry about aerodynamic loads on electric flap motors when the aircraft is parked at the gate or in a hangar?).>Ian, as a pilot we have no information regarding overheating >of the alternate flap motor. Thanks for the tip, HP (I guess the warning is mainly for engineers, to stop us repeatedly cycling the flaps during ground maintenance checks). Perhaps they don't give pilots this information because you wouldn't normally operate the flaps for longer than four minutes anyway.Cheers.Ian.

Just found this note in the Boeing Maintenance Manual regarding flaps in Alternate mode...(paraphrasing) In Alternate mode, the flap position sensing system doesn't have the same degree of accuracy as flap position sensing in normal Hydraulic mode, and, at Flap 30, the Flap Position Indicator pointers may not go into the white band/area (even though the flaps are in the correct position).Are flight crews warned about this? I'm thinking that they may be advised not to use Flaps 30 in Alternate mode because of this inaccuracy (i.e. they won't be able to confirm that their flaps have reached the required setting).Thanks.Cheers.Ian.

Another explanation could be that since the alternate flaps retract so slowly, it's not good to have the flaps fully extended if a go-around is needed.Doing some "training" with PIC, I ran into a nasty combination: The gear not being down and safely locked (which calls for flaps 30), and having to use the alternate flaps because of hydraulic leaks (which calls for flaps 20).I landed using flaps 20.Martin767 fetishistIt's a lot like life and that's what's appealing

Here is the WEALTH of knowledge provided to us in the ops manual on the matter."The alternate flaps selector extends and retracts the flaps and slats. Alternate mode flap and slat extension is limited to flaps 20. Extension of the flaps and slats from UP to position 20 requires approximately 3 minutes. Trailing edge flap asymmetry protection and flap load relief are not available in alternate mode. Slat and flap operation time in the alternate mode is greatly increased"And thats it...All non-normal checklists involving the use of alternate flaps simply state "use flaps 20 and Vref 20 for landing", no explanation given.

So do you think my explanation is reasonable? Because going around with flaps 30 isn't very good, is it?Martin767 fetishistIt's a lot like life and that's what's appealing

>Here is the WEALTH of knowledge provided to us in the ops >manual on the matter. >"The alternate flaps selector extends and retracts the flaps >and slats. Alternate mode flap and slat extension is limited >to flaps 20. Extension of the flaps and slats from UP to >position 20 requires approximately 3 minutes.G'day, HP.I find this quite amazing. Time for another letter to the specialists, methinks ;-) You would think that in an emergency situation, where this is no possibility of a go around (e.g. not enough fuel for a go-around), the pilot's manual would at least give you the option of making a Flap 30 approach into an airport with a short runway. I suppose the odds of having a flap hydraulic drive problem and a low fuel problem are considered too remote to consider?BTW, I got myself into an interesting situation the other day in PIC... ran very low on fuel somewhere over Newfoundland (I think) and realised that the engines were burning way too much fuel even at idle, to make it to the nearest airport, so, with a few hundred Kg of fuel remaining in the tanks, I powered up the APU and shut down the engines. This gave me everything (all electrics, hydraulics and pneumatics) but thrust. I don't know if this method is approved however .... I'd have to do a bit more investigation before I recommended this technique to real pilots :-) For example, I would have to figure out the glide ratios for idling and windmilling engines, figure out if the #2 tank fuel pickup for the APU is low enough to operate the APU at values of less than one tonne, etc, etc). Unfortunately, in my scenario, the only airport within gliding range was "CZUM". A deadstick landing into this airport is almost like landing on an aircraft carrier (the runway is not the longest... and at both ends, steep cliffs.... and no room for errors... Only recommended for thrillseekers and desperados :-hah). Cheers.Ian.P.S. By the way, if you want to know as much about these systems as I do, and seeing that we do work for the same company (although the manuals don't always reflect this), I might be able to lend you a good book on the subject ;-) Just e-mail me for more details.

I seem to recall that reasoning for flaps 20 on alternate but it isn't in the Boeing manual or SMAC guidelines we use.I think before I recommend an APU only approach I'd recommend watching the fuel gauges...(chuckle) Timothy

On the Boeing issued 737-200 manual they do go into a "song & dance" about Alt-source flaps 20 vs reduced retraction speeds on go-arounds.The 757s (both airline and Boeing's original) manual says just Flaps 20 on approach with alt-source extension without saying "why". Maybe the tech writer was paid by the word.Timothy

>Maybe the tech writer was paid by the word.LOL.....Either that or they ran out of room in the cockpit for bigger manuals ;-)BTW, my engineering training manuals for the 747-400 alone fill a large cupboard (I can't quite believe they squeezed these and the training manuals for the 747 Classic and the 767 onto a single CD!) Time to go digital perhaps? (Perhaps give the pilots a laptop or an extra screen in the cockpit for this sort of thing, a-la the 777? Maybe you could even update the manuals via ACARS? :-))Cheers.Ian.

>Time to go digital perhaps? (Perhaps give the pilots a >laptopSome airlines do that. Otherwise I wouldn't have these handy PDF manuals. ;-)Martin767 fetishistIt's a lot like life and that's what's appealing

It is nice to know there is a large source of technical knowledge out there on this forum. If I were flying this flight, I would first want to find out if the "MEL" (minimum equipment list)would allow me to continue and if so, would it be a wise choice.It appears that the MEL as well as the company's operation manual which is based on FAR Part 121 and a host of various federal regulations did allow this flight to continue. Other than lossing some time on the climb out and some addtional planning for the approach into SLC, it appears this flight was successful and made Delta some profit and hopefully got the passengers to their destination on time.My question is, without knowing the full extent to what was causing the problem, is it reasonable to fly nearly half way accross the country and hope that you can make a safe landing? I realize that SLC is a major Delta hub and should have the same maintenace capabilities as ATL but is this putting the passengers to a higher degree of risk? I too had a similar experience on Delta back in the 80s on a B-727 flight from FWA to IND, a distance of aproximately 119 NM. It was winter and we were IMC (in the clouds) for the entire flight. During the climbout and cruise, the flaps were cycled over and over which gave me and other passengers some concern in the cabin. I believe our cruise altitude was a lofty 8000 feet and time of flight was aproximately 20 minutes which is a lot less than a trip halfway accross the country.We landed with blowing snow and 1/2 mile vis (maybe) and taxied to the gate. Since I had some time till my connecting flight left, I hung around the gate and when the crew came off, I asked the F/O what the problem had been. He said that they could not tell if the flaps had retracted fully so that is why they were cycled repeatedly. I told him yes they appeared to be up and if he had doubts, why did he not send the F/E back to make a visual observation. I told him he had a spooked cabin when the flaps where going in and out. Maintenance found a defective flap position transmitor and replaced it prior to that flight continuing on to Florida. With my flight, going to the destination made sense to a point. Connecting flights and maintenace would be better but the weather was worse and could have been a factor if indeed we did have a IFE (in flight emergency).Terry