This tongue-in-cheek disparaging claim about our beloved trijet came up in another forum recently.The situation : You're flying from A to B, and get told for whatever reason to be at a certain altitude when 35nm from a VOR that isn't part of the route, and is about 20 miles off the route. (edit: The A-B route is part of a STAR and cannot be changed. We don't want to go to the new VOR, we just need a waypoint on the existing route at a point 35 miles away from it so we can put an altitude restriction in there) The claim : On the MD-11 you need pen and paper and a calculator and need to manually work out when that point will be. Naturally I didn't believe that, but I've been trying and have to say I've not found an easy way to do it ...Here's how you do it on the 747, there must be an easy way to do it on the MD !! :( Say you get told to report 35nm from the NP VOR (we don't need 3 letter names down here, in fact to be honest we don't even need 2 letter names :()First a quick trip to the Fix page, and plot the NP VORThen add a 35nm ringLSK the waypoint into the scratchpadChange to the Legs page and LSK again to insert it into the routeClose the discon, activate the route, get rid of the fix to make it look tidy, and hey presto there's the waypoint 35nm from NP ready to have the crossing restriction applied. Took about 45 seconds to do it ...So ... How do I do this in the MD-11 ??? :( ThanksGary

Easy, enter a Lateral Revision Waypoint (FMS100.6) then clear the disconntinuity, this sets up the segment to NP VOR, now enter a Along Track waypoint (aka place-distance FMS100.1) to put the 35nm before NP waypoint in the path then use the Vert Rev page at that location to enter an altitude constraint (FMS 50.7). No pencil, paper or calculations necessary.

But that changes the route and takes us via NP.[polite] I may have neglected to mention this, but [/polite] NP is not part of the route, we don't want to go there, we just need a waypoint 35 miles from it on the current route - exactly as shown on the 747 screenshots.CheersGary

Ah, I missed that complexity. I wouldn't know how to do this with the MCDU, obviously it does not draw arcs or circles. Is this a real world problem?

Ah, I missed that complexity. I wouldn't know how to do this with the MCDU, obviously it does not draw arcs or circles. Is this a real world problem?

It was while flying a STAR with online ATC, so presumably it happens in real world as well. Of course, in the real world there would most likely be a proper intersection there ... But it must arise at least occasionally, otherwise why would the Boeing make it so easy ?GaryHmm, arcs ... I wonder if you could do something with route 2 and a DME arc ? Probably not in 45 seconds .....

If I ran up against this flying something with steam guages, I would look at the chart and either find a fix there or estimate a place-distance using the scale on the chart and the pencil... could also ask for ATC for a DME fix in lieu of the off route distance clearance... I've only been flying IFR for 28 years so my experience is limited but I would definitely let ATC help out.

The MD-11 and the 747-400 (and the 767-300) were all introduced within a couple of years of each other, none of them are exactly steam gauges.As it happens my reply in the other forum was along the lines of "ATC is obviously looking at a certain spot on his screen and knows where it is relative to the VOR, ask him for the bearing to the VOR from that point." :( I'd still like to know how to do it in the MD-11 using the onboard computers though ...CheersGary

Yeah this is one of the biggest downfalls of the MD11 for me, I love the plane but it lacks a couple important (IMO) navigation features other aircraft have.

Yeah this is one of the biggest downfalls of the MD11 for me, I love the plane but it lacks a couple important (IMO) navigation features other aircraft have.

But how often does a situation like this really happen though? I doubt it's that common.

But how often does a situation like this really happen though? I doubt it's that common.

Well, I'll fly the route again, and see if the controller gives me the same crossing restriction.Hey there Chairman! :( I think it's a perfectly reasonable clearance to give an RNAV equipped aircraft. It would have been hairy in an older plane though, since the VOR only had a 60nm range. Like I said on the "other" forum. It was a simple matter of doing some math to make the crossing restriction, since the distance was on the FIX page. I think very few people would have said "unable". I'll have a look at the chart and see if there is any alternate means of identifying that point.It seems odd that the MD won't draw rings though. I'm told that the older 767's with standard FMC's can't either. If my memory serves me well, it's because of a hardware limitation that would cause the unit to crash if it tried to draw the number of lines needed to create a circle.Paul

I think it's a perfectly reasonable clearance to give an RNAV equipped aircraft

I haven't looked in 7110.65 in about a year, so I had to reopen it to look for this... but I gotta tell you, I don't think an FAA controller is going to issue this type of clearance (ref section 5 para 4-5-7). As I said earlier, I wouldn't hestiate to ask ATC for a crossing radial or DME distance to put a waypoint on my route ahead, but as Paul said there's no need to stoop so low as to declare unable.

I haven't looked in 7110.65 in about a year, so I had to reopen it to look for this... but I gotta tell you, I don't think an FAA controller is going to issue this type of clearance (ref section 5 para 4-5-7). As I said earlier, I wouldn't hestiate to ask ATC for a crossing radial or DME distance to put a waypoint on my route ahead, but as Paul said there's no need to stoop so low as to declare unable.

Correct.In this situation, the VOR being not even close to the route, a more professional request from ATC would be:To cross Radial rrr, VOR xyz, AT or ABOVE/BELOW.Easy to enter in the MD11 FMS too.Regards,Harry

I'll have a look at the chart and see if there is any alternate means of identifying that point.

Hi Check :( Which STAR is it ? My next thought, hard on the heels of "ask the controller for the bearing", was that if this is a normal procedure then there surely has to be an intersection there - it would be a bit odd asking every plane that came in that way to be at 12,000' by 35nm from XYZ but completely normal asking them to be at 12,000' by LIMBO or whatever ...ps - I concede defeat on this one - sounds like there is no easy way to make the MD-11 do the calculation for you :( CheersGary

Hi Check :( Which STAR is it ? My next thought, hard on the heels of "ask the controller for the bearing", was that if this is a normal procedure then there surely has to be an intersection there - it would be a bit odd asking every plane that came in that way to be at 12,000' by 35nm from XYZ but completely normal asking them to be at 12,000' by LIMBO or whatever ...ps - I concede defeat on this one - sounds like there is no easy way to make the MD-11 do the calculation for you :( CheersGary

Gary,If crossing the circle twice at a 35nm from the station, what point does ATC have in mind?If ATC states to cross a radial from the station, only one point is left.Regards,Harry

The VOR in question was pretty close to the airport, and it was clear what "side" of the VOR had the restriction. I checked the chart and there's no fix at that point.Here's a mental picture though:VKZ is about 8 miles east of KMIA. Descending on the CYY5 arrival (from the west), the controller says "cross 40nm west of VKZ at 10,000). A 40nm ring intersects the route at one point only, but we can't get the FMS do draw us a picture.It needs a bit of careful calculation, but it's doable. I can't say the clearance bothered me. In the good ol' days flying the three holer (727), I'd have done it just the way any MD11 pilot would have to.Paul