Obstacle Departure Procedures

[M-crit]

I recently encountered an obstacle DP that simply says “RWY 5, Climbing left turn direct ABC VOR.” At what altitude do you start your turn? Is it as soon as practicable? Is it at 400 ft agl since if there is no published ODP, obstacle departure procedures are based on the pilot climbing to 400 ft above the departure end of the runway before making an initial turn? For discussion purposes, let’s assume a 0/0 takeoff under part 91 in mountainous terrain.

Also, say you are 30 nm out on a feeder route inbound to the IAF in uncontrolled airspace. ATC says “cleared approach” and you are currently at 5000 ft. The feeder route has an MEA of 4000 ft. Do you have do descend right away to 4000 since you have been cleared approach, or can you stay higher until closer to your IAF?

 

[Flyerjosh]

I recently encountered an obstacle DP that simply says “RWY 5, Climbing left turn direct ABC VOR.” At what altitude do you start your turn? Is it as soon as practicable? Is it at 400 ft agl since if there is no published ODP, obstacle departure procedures are based on the pilot climbing to 400 ft above the departure end of the runway before making an initial turn? For discussion purposes, let’s assume a 0/0 takeoff under part 91 in mountainous terrain.

400' is the lowest minimum altitude to make the turn, unless otherwise indicated on a procedure or takeoff performance data (Such as Aerodata or JeppData)

Also, say you are 30 nm out on a feeder route inbound to the IAF in uncontrolled airspace. ATC says “cleared approach” and you are currently at 5000 ft. The feeder route has an MEA of 4000 ft. Do you have do descend right away to 4000 since you have been cleared approach, or can you stay higher until closer to your IAF?

Yes, assuming that they didn't give you any new altitude restrictions, you may stay at the last assigned altitude (5000') if desired, until you choose to descend.

 

[MALSR]

You cannot remain at the last assigned altitude if you have been given approach clearance and are established on a published portion of the IAP that is indicating a lower altitude. In this case the published altitude applies, not the previously assigned altitude. See AIM 5-5-4 and 5-4-7

 

[Catbert]

You cannot remain at the last assigned altitude if you have been given approach clearance and are established on a published portion of the IAP that is indicating a lower altitude. In this case the published altitude applies, not the previously assigned altitude. See AIM 5-5-4 and 5-4-7

Wrong. (politely)

Both areas of the AIM you quote state that unless otherwise directed by ATC, the published altitudes now apply. This part we agree on. However, the published altitudes on feeder routes are usually (maybe always?) minimums. If you want to fly it higher, fine. For reference, look at the Planview Symbols legend in the NOS approach plates (page G1). You'll notice that at the top left it shows approach segments and feeder routes. The altitudes are shown as minimums.

This would apply to other segments as well. Lets say you are getting vectors to the ILS: you are cleared for the approach and told to maintain 4000 until established on the localizer. If there's a minimum altitude of 3500 for that segment of the localizer, you can descend to that once established. But it's not required.

Sometimes a mandatory altitude is published. In that case, you're obviously required to use that alitude.

 

[avbug]

I recently encountered an obstacle DP that simply says “RWY 5, Climbing left turn direct ABC VOR.” At what altitude do you start your turn? Is it as soon as practicable? Is it at 400 ft agl since if there is no published ODP...

You encountered an obstacle departure proceedure, but want to know when to start if there is no obstacle departure proceedure? I don't understand your paragraph...you state there is an ODB, and then state there is no ODP.

All departures are predicated on crossing the departure end of the runway at 35', and climbing to 400' before starting the turn. If no obstacles penetrate a climb in any direction in a 40:1 obstacle clearance plane (also called obstacle identification surface, then the airport has what is called "diverse climb criteria," or a "diverse departure assessment." In this case, no obstacle departure is published.

All departures assume at least a 200'/nm climb gradient, including diverse departure criteria.

If obstacles penetrate the 40:1 plane in any direction, then a departure is published. The departure may make use of increased climb gradients, routing, etc.

If no minimum altitude is provided prior to starting your turn, then the minimum altitude is 400, and will not be published. If no minimum climb gradient is published, then the minimum climb gradient expected of you is 200'/nm.

An important consideration is that while the minimum diverse climb gradient is 200'/nm, the 40:1 obstacle clearance plan is a 152'/nm gradient. What that means for you is that if you just make the minimum climb gradient, you may be clearing obstacles by definition, by only 48'/nm. That's not a lot. If you calculated your climb gradient based on your departure speed (a reasonable effort), a departure with a turn downwind provides you a higher groundspeed and a lower climb gradient as a result...that 48' magically goes away quickly.

The 40:1 obstacle identification plane extends from the surface right up to the minimum IFR altitudes, for planning and departure design purposes.

For discussion purposes, let’s assume a 0/0 takeoff under part 91 in mountainous terrain.

Really quite irrelevant, as the departure is what it is. What is published is what you fly. Mountainous terrain, flat land, off an island, with green eggs and ham. If you don't see a published climb gradient, you have 200'/nm minimum. The only time your visibility comes into play is VCOA departures, which are Visual Climb Over Airport obstacle departures. These require specific visual climbs above the airport or to a navaid. Some departures, including both VCOA and non-VCOA departures, have preset visibility requirements to permit pilot visual identification and avoidance of obstacles in the event the minimum climb gradient is compromised (such as might be the case in an engine failure).

Occasionally a departure may also be predicated in one respect or another on what are called Low Close in Obstacles. These are less than 200' and within a mile of the runway, do not require increased takeoff minimums, but may require special departure proceedures. These will require that the pilot see and identify the object at a specified point and altitude.

You cannot remain at the last assigned altitude if you have been given approach clearance and are established on a published portion of the IAP that is indicating a lower altitude. In this case the published altitude applies, not the previously assigned altitude. See AIM 5-5-4 and 5-4-7

As Catbert properly noted, the above quote is incorrect. You unless assigned an altitude, the published altitutes on the approach are minimum altitudes, not mandatory altitudes. If you have been assigned an altitude and are subsequently cleared onto an approach, the published altitudes apply as the minimum altitudes.

If you are cleared via an arrival, you are still expected to maintain ATC issued altitudes, unless specifically given the clearance "descend via" the arrival...in which case you are expected to comply with published altitudes for the arrival. A descend-via clearance is not part of an approach; you are expected to maintain the last assigned altitude until established on the approach, at which time you may descend to the minimum applicable altitude for the segment of the approach for which you are flying.

Also, say you are 30 nm out on a feeder route inbound to the IAF in uncontrolled airspace. ATC says “cleared approach” and you are currently at 5000 ft. The feeder route has an MEA of 4000 ft. Do you have do descend right away to 4000 since you have been cleared approach, or can you stay higher until closer to your IAF?

In this case, unless ATC instructs you to descend to 4,000, then 4,000 represents your minimum altitude. The approach clearance should sound something like "Boomer Uglybottom Five Five, maintain five thousand until established, cleared the RNAV 36 Approach at Tehachialpeguichiquiddich, report down time on this frequency." Because you weren't given a specific fix, you may begin the approach at any fix. If you're headed for a fix that starts the approach and the minimum altitude after that fix is 4,000, you may start down to 4,000 any time after passing that fix. When you start down, how you do it, and how if affects you ability to live a long life filled with religious fullfillment, is entirely up to you.

 

[xdays]

Avbug,

What a great explanation you offered. Started out a little too technical for a simple mind like mine, but you made a great recovery! So, where exactly is "Tehachialpeguichiquiddich" ? :laugh: Great Job!!

 

[avbug]

"All departures are predicated on crossing the departure end of the runway at 35', and climbing to 400' before starting the turn" is too complicated?

I'm glad I watered it down.

Tehachialpeguichiquiddich is thirty miles south of the Arapajanoviskionicovac county line west of Winchestertonfieldville, on the highway between Tehachialpeguichiquiddichapany and Tehachialpeguichiquiddichophollis. About an hour north of Yazoo city, for those who aren't familiar.

 

[A Squared]

All departures are predicated on crossing the departure end of the runway at 35', and climbing to 400' before starting the turn.

One small nit to pick. There are some departures which state "turn right as soon as practical" or "immediate left turn" I fly to a few airports like that. In such a case, I wouldn't wait untill 400 AGL before starting a turn, especially in a slow climbing aircraft.

 

[avbug]

Reference AIM Chapter 5, section 2, para 5-2-6:

In rare instances, obstacles that exist on the extended runway centerline may make an "early turn" more desirable than proceeding straight ahead. In these cases, the published departure instructions will include the language "turn left(right) as soon as practicable." These departures will also include a ceiling and visibility minimum of at least 300 and 1. Pilots encountering one of these DPs should preplan the climb out to gain altitude and begin the turn as quickly as possible within the bounds of safe operating practices and operating limitations. This type of departure procedure is being phased out.

Most important to know about this type of proceedure is that the instructions to turn early will be published with the proceedure, and as with any proceedure, it is what it is. One may require flying to a particular altitude before turning, another to a particular fix before turning. Some may prescribe early turns, specific climb gradients, etc...the proceedure is what it is, and no generality precludes adhering tenaciously to the proceedure.

 

[xdays]

"All departures are predicated on crossing the departure end of the runway at 35', and climbing to 400' before starting the turn" is too complicated?

I guess you didn't see the tongue in my cheek .

Tehachialpeguichiquiddich is thirty miles south of the Arapajanoviskionicovac county line west of Winchestertonfieldville, on the highway between Tehachialpeguichiquiddichapany and Tehachialpeguichiquiddichophollis. About an hour north of Yazoo city, for those who aren't familiar.

I think I've been there! UGLY women