Quote:
Originally Posted by juice
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?
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Very good question.
The answer is based on our route. We are filed on Miera two arrival. the transition segment from CME to CNX is 12000 MEA 9000T and from CNX to Miera it is 12000 MEA 10000T. Now lets back up we are in Houston in 53000 pound XR. Our burn to ABQ will be approx 5000 pounds I based this on a burn of 1:40 minutes. Now looking at page 1-42 in the FOM none of this is based on being able to navigate soley on land based Navaids which brings up the FMS. I will get back to that in a moment(bare with me). To sum up 1-42 in a nut shell you must be able to maintain an altitude of 1000ft above the tallest obstacle in mountainous terrain within 5 miles of your route at a specific weight(limited at takeoff & more restrictive then Drift Down). If you can't maintain the 1000 ft clearnce then you are dispatched under DD. Now if our FMS is MEL'd everything I am about to say WOULD BE invalid at the temperature I chose because we will not be assured obstacle clearance off of the MOCA altitudes listed above. Now go to the ENROUTE NET CEILING chart. You referenced page 5-9 in the volume 1 which is the answer to the question * Enroute Net Ceiling. Lets say the burn from IAH to CME is 4000 pounds(I am sure it is more than this with winds) 53000 - 4000 = 49000. ISA + 30 is 10900ft. Now MOCA from CME to CNX is 9000T and CNX Miera is 10000T we meet this requirement at ISA + 30 and with the FMS operative. Look at 5-8 in the volume 2 ENROUTE LIMITATIONS: One Engine Inoperative the bottom of paragraph a. "based on the ambient temperatures expected enroute". I highly doubt that anything above ISA + 25 would fall into this category " based on ambient temperatures expected enroute" for this route. I think the highest ISA I can recall is +15.
Now you got me thinking if your FMS was MEL'd or failed during your flight to ABQ you would definetally need a little more attention to your route in the planning phase and enroute phase. Planning phase would require abiding to the MEL a) Current Aeronautical Charts are used to verify Navigation Fixes prior to dispatch b) Procedures are established and used to verify status and suitability of Navigation facilities used to define route of flight c) approach navigation radios are manually tuned and identified. So in other words the example I used at ISA+30 with a Mel'd FMS would not be valid since MOCA would not assure us acceptable navigation coverage more than 22 nm from the VOR which is why I think this route is assumed to be at or less than ISA+25 using the Enroute net ceiling chart. From p 5-8 paragraph a) " based on the ambient temperatures expected enroute"