TC/DD question

juice · 01-31-2008, 12:00 AM

according to our high altitude enroute charts, airways with the brown are: "route segment over terrain equal to or exceeding 8000' msl. This route segment is part of DD/TC procedure"

per the FOM, routes with terrain over 8000 will have DD/TC info (page 5-9)

for IAH-ABQ or ABQ-IAH we are filed over J15 which is brown from ABQ to CME.

there are no DD/TC charts in the perf. manual for this city pair and we have no mention of dd/tc on the release.

how is this possible?

junglejetman · 01-31-2008, 12:31 AM

I would guess the route is automatically displayed in brown between ABQ and CME by Jeppessen, because of the thin band of mountains that rise over 8,000 feet just east of ABQ. But pretty much every where around there the rest of the terrain is much less (5,000 or lower as you head east). So you don't need a DD or TC release. If an emergency happened when you were over those mountains, you'd just go back to ABQ or press on to the east, and would be clear of all high terrain either way.

But I could be wrong.

kidicarus5897 · 01-31-2008, 12:54 AM

Asked the same question. Dispatch told us that the mountains arn't within 5nm of the course, so no DD or TC was necessary............sounds reasonable

juice · 01-31-2008, 01:34 AM

Quote:

Originally Posted by kidicarus5897

Asked the same question. Dispatch told us that the mountains arn't within 5nm of the course, so no DD or TC was necessary............sounds reasonable

if you look at the 10-1 page for ABQ, it shows J15 in green, it goes almost directly over a 9500 ft peak, and a 8100 slightly north of that. so i don't know how they figure it's not within 5 miles... the route listed on the flightplan is ABQ..CNX which is the same as J15.

kidicarus5897 · 01-31-2008, 01:56 AM

Quote:

Originally Posted by juice

if you look at the 10-1 page for ABQ, it shows J15 in green, it goes almost directly over a 9500 ft peak, and a 8100 slightly north of that. so i don't know how they figure it's not within 5 miles... the route listed on the flightplan is ABQ..CNX which is the same as J15.

I take that back. What I meant to say was that, according to dispatch, there is terrain less than 8k within 5 nm to one side of the route. I guess that means that it doesn't require TC or DD consideration

juice · 01-31-2008, 02:02 AM

Quote:

Originally Posted by kidicarus5897

I take that back. What I meant to say was that, according to dispatch, there is terrain less than 8k within 5 nm to one side of the route. I guess that means that it doesn't require TC or DD consideration

i understand what they told you, but i'm saying it's clear that that is not the case, looking at the 10-1 there IS terrain within 5 miles of J15 above 8000ft. now, i'm not blaming dispatch, they don't make the performance data....

so i'm still curious how it is excluded....

kidicarus5897 · 01-31-2008, 02:09 AM

Does that 8k terrain cover ALL 10nm latteraly across the airway? Or is there some point within 5nm either side of the airway that is less than 8k where you are talking about? If not, I would get a hold of someone who makes these charts and whop some ***

juice · 01-31-2008, 06:57 PM

Quote:

Originally Posted by kidicarus5897

Does that 8k terrain cover ALL 10nm latteraly across the airway? Or is there some point within 5nm either side of the airway that is less than 8k where you are talking about? If not, I would get a hold of someone who makes these charts and whop some ***

i'm not sure what you are getting at exactly... are you saying that say the peak is only on the left side of the airway (but within 5 miles) that is OK... you could just fly the right side of the airway? this is not legal per the FARs and the FOM... page 5-8...

bluedevils · 01-31-2008, 09:32 PM

Without seeing the routes Dispatch files ... for arguments sake I'll assume they DON'T file J15 between ABQ & CME -- but use CME as the initial fix on departure / last fix on arrival. In this case, ABQ J15 CME wouldn't be a 'route segment' & I guess radar vectors on departure / arrival would be planned for. In either case, you'd be on this 'route segment' - if flown - well below the valid altitude for using DD / TC anyway (i.e. in initial climb or in descent). Perhaps TOC or TOD points even have something to do with it. In any case - great question ....

Yariv · 01-31-2008, 10:49 PM

Quote:

Originally Posted by bluedevils

Without seeing the routes Dispatch files ... for arguments sake I'll assume they DON'T file J15 between ABQ & CME -- but use CME as the initial fix on departure / last fix on arrival. In this case, ABQ J15 CME wouldn't be a 'route segment' & I guess radar vectors on departure / arrival would be planned for. In either case, you'd be on this 'route segment' - if flown - well below the valid altitude for using DD / TC anyway (i.e. in initial climb or in descent). Perhaps TOC or TOD points even have something to do with it. In any case - great question ....

another way of saying the same thing is to say that TC/DD data is required for routes where 8k terrain is found AT CRUISE. meaning between TOC and TOD. or at least above the valid altitude. if you lose an engine after TOD, you'd be able to descend/drift down to the destination.

I'm not positive this is the case for this specific example, because what if you lose an engine on the way to ABQ before TOD and without any DD alternates or escape routes published you elect to continue, and now the terrain may be in your way and your ceiling below it... not likely since you're probably at or below MGLW at this point.

send a message to GS... maybe this route does require TC/DD.

the point about the airway being 5 miles wide on either side is not valid in my opinion. airway width causes things to be MORE restrictive, not less. it means that terrain has to be less than 8k anywhere in the 10 mile width, rather than saying that as long as any part of the width is below 8k it's ok...