dragon Posted March 3, 2003 Share Posted March 3, 2003 Why is it that the Boeing 767 300 operating manual prohibits a single engine taxi ‘out’ but permits a single engine taxi ‘in’ as opposed to the 200 where single engine taxi is permitted both ways? Of course the sensible answer is steering stresses and weight. Keep in mind the wingspan [200 v 300]is identical, as is the position of the engine on each wing. The total length from main truck axle to the nose wheel axle is an additional 10 feet on the 300 [11 feet to the horizontal stab as well], the AOM makes no mention of a weight restriction. Anyone? Link to comment Share on other sites More sharing options...
Guest George Posted March 3, 2003 Share Posted March 3, 2003 Boeing doesn't recommend single engine taxi-out on any 767 for: workload reasons and additional operational procedures....Plus the engines need several minutes to warm up prior to takeoff. Keep in mind that the Boeing FCTM (flight crew training manual) is written for the lowest common denominator in aircraft operators. The -300 is can be quite a bit heavier and its engines are significantly more powerful. Revving up a PW4060 or GE CF6 while single engine taxiing may cause a lot of problems to equipment and personnel on the ramp. There may be changes that allow SE taxi under specific conditions ie a max wgt etc....in the not too distant future. Link to comment Share on other sites More sharing options...
Mitch Cronin Posted March 3, 2003 Share Posted March 3, 2003 I'll guess dragon... I think you hit on it with the distance to the nose... There'll be additional side loads on the nose gear oleo that may be considered too much with a loaded -300. When you apply any breakaway thrust with only one engine, the nose wheel sits there resisting the aircraft's attemp to pivot on the other main, the greater the weight of the bird, the greater thrust required, and the more torque that the nose gear has to resist. I know 10 feet doesn't seem like a lot, but when you consider the increased torque applied because of the 10', it begins to make me wonder why it's ok even with an empty ship. Cheers, Mitch Link to comment Share on other sites More sharing options...
dragon Posted March 3, 2003 Author Share Posted March 3, 2003 Not ‘recommends’ and not ‘FCTM’, but the Boeing AOM states “a minimum of 5 minutes prior to takeoff, to ensure time for warm up,……” There is only one Boeing limitation, re: engine oil temperature and advancement of thrust levers for takeoff. 50 degrees for PW 4060 engines only. [even on the coldest of days, a matter of seconds, not minutes] What is heavier, a fully loaded 200 with JTD-9 engines or a 300 with 4060s fuelled for a 200 mile rapidair? If there are personnel or equipment it will cause damage as well and yet the Boeing 767 AOM ‘permits’ single engine taxi, warning included. Your statement therefore is not accurate, IMO Boeing begins with the cursory warning about injury to personnel and equipment, after that, it directs the decision to taxi single engine, to the captain, conditions apply, including the 300 series, taxi ‘out’ only. Finally, any idea why “There may be changes that allow SE taxi under specific conditions, ie a max wgt etc....in the not too distant future.”? Still curious Link to comment Share on other sites More sharing options...
dragon Posted March 3, 2003 Author Share Posted March 3, 2003 Heh Mitch, I was hoping to get the resident technical expert involved. I will buy your torque argument. Though as I stated, there are restrictions to the 200 taxi out, there are no weight caveats included except ”Heavy aircraft weights such as those encountered in overseas operations”, after that we default to ‘Captain’s discretion’ Re, the 10 feet. It is not OK on an empty ship [300 only] outbound, but it is OK to taxi a 300, single engine inbound, regardless of the weight. Does not make sense to me?... Link to comment Share on other sites More sharing options...
Guest George Posted March 3, 2003 Share Posted March 3, 2003 You refer to the Boeing AOM, what are you talking about? The Boeing Ops Manual? What edition????AC AOM?????? I agree with your point about wgts, that's why some guidance about single engine taxi may be forthcoming, for AC flt crew....I am assuming your work for AC.... Link to comment Share on other sites More sharing options...
Mitch Cronin Posted March 3, 2003 Share Posted March 3, 2003 I've been puzzling over this one since I read your post this morning and I can't think of a better explanation. Like all of them, Boeing gives us warnings about damage to nose gear and seals in the nose oleo if we run one at high power without ballancing it with power on the other wing, but I'm stuck on why only "In" vs "Out" is mentioned, and no weight? It's as though they're just assuming all outbound taxiing is done heavier than inbound. My hunch is that they just felt it better to let you trash the seals on the way in rather than have you headed off into the wild blue after having done so. ?? ?? Landing with a flat nose oleo would be... uhhh, ..rather uncomfortable. What else changes, inbound vs outbound? You could be headed out with virtually the same load another guy is headed in with, (I think that's what you were trying to tell me) depending on this, that and the other thing... brakes while coming in will be hotter, but for this question, so what?... I might be wearing blinders, but it's only that the outbound guy doesn't get a chance for someone to see the mess by the nose gear that seems to make the difference between in and out. Link to comment Share on other sites More sharing options...
dragon Posted March 3, 2003 Author Share Posted March 3, 2003 The Air Canada issued 767 Aircraft Operating Manual, amended to the current transmittal, 15. Yes, I work for AC. Is this AC specific and if so, do you know what the reasoning is? Link to comment Share on other sites More sharing options...
dragon Posted March 3, 2003 Author Share Posted March 3, 2003 Thanks Mitch, I agree, it is vague and nonsensical to me as well. Shall we mark it down to one of those “Local [uL] phenomena” ? cheers Link to comment Share on other sites More sharing options...
Guest jimmy Posted March 3, 2003 Share Posted March 3, 2003 A couple of thoughts: Yes you will, in most cases, be lighter on the way in so less power from the one engine etc. and also since you are coming in you will probably in motion so no great amounts of power to break away. Just a bit to keep moving. The AC manual states that two engine taxi "should" be used... If it is safe to do so (very low weight) you could taxi out on one on a -300. "Should" doesn't mean "must". It doesn't seem nonsensical to me. It is just guidance, hence to term "should". If you want to know for sure, call Ed. Jimmy Link to comment Share on other sites More sharing options...
dragon Posted March 3, 2003 Author Share Posted March 3, 2003 Jimmy, Where does the manual say it “should”, except that you “should” taxi a 300 ‘out’ with two engines, and where does it say you ‘could’ taxi out on one on a 300? Why does the manual state that the second engine IS ALWAYS to be started at this time [initial start] on a –300 [1.04.03 P. 7] Your point about weights is moot – manual [ly] speaking. The manual I have says nothing about “very low weight” , that is your interpretation if you will?. It goes on to talk about restrictions, including congested ramp areas and repeated break away thrust etc. Would it not follow then that the majority of the 767 network would be restricted from single engine taxi, period? In YZ, with all factors considered, it is not unreasonable to require breakaway thrust 5 or 6 times landing 05/23 and taxiing to either an OVS or a DOM gate. It seems nonsensical to me or incomplete at best. A little guidance would be contained in print, along with the other full page of text, hence the term “may” along with “except that two engine taxi OUT, SHOULD be used on a 300 aircraft.” [1.04.03 P1] dragon Link to comment Share on other sites More sharing options...
Guest jimmy Posted March 3, 2003 Share Posted March 3, 2003 OK, as I read 1.04.03 P1, it seems to give some latitude; as I said earlier, "should" vs. "must". However, at the bottom of 1.04.03 P7, "note: The second engine is always to be started at this time on the -300", seems to take away the option. I agree there is a contradiction there. Call Ed. Maybe they need to clarify it for all. Jimmy Link to comment Share on other sites More sharing options...
dragon Posted March 3, 2003 Author Share Posted March 3, 2003 I'm too much of a sh*t disturber on this forum. I could ask but then I'd be outed. Why don't you send him a note and clear it up then ask him to clarify for all of us interested in saving a little fuel every time we taxi around the maze. cheers Link to comment Share on other sites More sharing options...
Guest jimmy Posted March 3, 2003 Share Posted March 3, 2003 Dragon, are you on the AC pilot's forum? Link to comment Share on other sites More sharing options...
dragon Posted March 3, 2003 Author Share Posted March 3, 2003 uh,..... maybe. Why? Link to comment Share on other sites More sharing options...
Guest jimmy Posted March 4, 2003 Share Posted March 4, 2003 This is an Air Canada specific topic. How about we continue over there. Link to comment Share on other sites More sharing options...
dragon Posted March 4, 2003 Author Share Posted March 4, 2003 jimmy, I am very careful not to discuss ‘Air Canada specific’ topics on this forum. This is a technical thread, a ‘767 specific’ thread, with a reference to a manual available on the internet. AC just happens to operate 767s., and there the topic overlaps somewhat. Start a thread over there if you wish, I’ll check in with you later. dragon Link to comment Share on other sites More sharing options...
IFG Posted March 4, 2003 Share Posted March 4, 2003 Ah ... Mitch - re: "the increased torque applied because of the 10' [longer on the -300 I assume]" - If Archie got it right back when he was figgering out levers and fulcrums, wouldn't the side load be less on the longer airplane (everything else being equal?) Cheers, IFG (hope it's OK to query on an "AC" thread ) Link to comment Share on other sites More sharing options...
IFG Posted March 4, 2003 Share Posted March 4, 2003 Ah ... Mitch - re: "the increased torque applied because of the 10' [longer on the -300 I assume]" - If Archie got it right back when he was figgering out levers and fulcrums, wouldn't the side load be less on the longer airplane (everything else being equal?) Cheers, IFG (hope it's OK to query on an "AC" thread ) Link to comment Share on other sites More sharing options...
DEFCON Posted March 4, 2003 Share Posted March 4, 2003 Maybe it's got something to do with fuselage stresses? Link to comment Share on other sites More sharing options...
Mitch Cronin Posted March 4, 2003 Share Posted March 4, 2003 Ah ... thanks for putting that so diplomatically. Ya, I s'pose I was thinking force x radius, ...increase radius =... but of course that's not the radius who's increase will do that... That'd be more representative of the load in a third class lever I think?... There's more than at first meets the eye here. Our "load" in this case changes depending on amount of force applied, doesn't it? ... Because the nose wheel is on the ground does it become a fulcrum instead of a load while insisting the aircraft go straight while taxiing? And if you increase the distance from force to fulcrum, I don't know how to measure it, or prove it right now, but haven't you just increased the torsional load on that fulcrum? I dunno? But I do know it's not a simple as the levers I can work out in my head at the moment. :S Link to comment Share on other sites More sharing options...
Mitch Cronin Posted March 4, 2003 Share Posted March 4, 2003 Ah ... thanks for putting that so diplomatically. Ya, I s'pose I was thinking force x radius, ...increase radius =... but of course that's not the radius who's increase will do that... That'd be more representative of the load in a third class lever I think?... There's more than at first meets the eye here. Our "load" in this case changes depending on amount of force applied, doesn't it? ... Because the nose wheel is on the ground does it become a fulcrum instead of a load while insisting the aircraft go straight while taxiing? And if you increase the distance from force to fulcrum, I don't know how to measure it, or prove it right now, but haven't you just increased the torsional load on that fulcrum? I dunno? But I do know it's not a simple as the levers I can work out in my head at the moment. :S Link to comment Share on other sites More sharing options...
Guest Soarcerer Posted March 4, 2003 Share Posted March 4, 2003 I'll never forget the musings of a flight-deck visitor many years ago. He had been up for a visit for a considerable time and was very eager to have many of his questions answered on various aspects of flying. Before he returned to his seat, he posed the following question to us: "...Ok," he said, I now understand what keeps us up here, and how how the reversers work, and how the engines engines push us along, but tell me; what powers the airplane and makes us move about when we are on the ground"????? "Are the wheels powered electrically or hydraulically"???? .... our silence was deafening....... Link to comment Share on other sites More sharing options...
IFG Posted March 5, 2003 Share Posted March 5, 2003 OK, Mitch - that reference to "third class" levers went over my head :s In the SE taxiing case, tho', fulcrums don't really have a role; more likely your focus on rotational force, or torque, was on the mark (with a bit of simplification of course). That being so, of course, in counteracting the turning tendency from a given number of ft-lbs produced by one engine, an increase in the # of feet to the nose-wheels would reduce the required lbs force applied in side load on the gear? I'm still curious about Dragon's inital question as to why there would be any difference in restriction between the -200 & -300, other things being equal? Cheers, IFG Link to comment Share on other sites More sharing options...
Mitch Cronin Posted March 6, 2003 Share Posted March 6, 2003 1st class lever - Load at one end, fulcrum in the middle, force to raise load on other end (eg. kids seesaw) 2nd class lever - Fulcrum at one end, load in the middle, force on the other end (eg. wheelbarrow) 3rd class lever - fulcrum at one end, load at other end, force in between (eg. most of our bones that swivel, or a paddle -man provides fulcrum with hand at one end) Depending where you did your early schooling, it may have been an eon or two since you learned that stuff, so you've probably forgotten it... introduced in grade 6 here. Yeah, I'm curious too. I think I fell into a trap there trying to cook up some reason for a policy that might be flawed (?)... It's not making any sense at all to me now. If it's thrust required to breakaway that's at the heart of it, you'd think they should be mentioning weights (along with cautioning use of throttle), not "in" or "out". And I'd think it should apply to the 200 as well... I'm stumped. But these days, I get that way pretty easy. Cheers, Mitch Link to comment Share on other sites More sharing options...
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