AIM 

4/20/23 

3. 

Design and publish a specific departure route; or 

4. 

A combination or all of the above. 

e. 

What criteria is used to provide obstruction clearance during departure? 

1. 

Unless specified otherwise, required obstacle clearance for all departures, including diverse, is based on 

the pilot crossing the departure end of the runway at least 35 feet above the departure end of runway elevation, 

climbing to 400 feet above the departure end of runway elevation before making the initial turn, and maintaining 

a minimum climb gradient of 200 feet per nautical mile (FPNM), unless required to level off by a crossing 

restriction, until the minimum IFR altitude. A greater climb gradient may be specified in the DP to clear obstacles 

or to achieve an ATC crossing restriction. If an initial turn higher than 400 feet above the departure end of runway 

elevation is specified in the DP, the turn should be commenced at the higher altitude. If a turn is specified at a 

fix, the turn must be made at that fix. Fixes may have minimum and/or maximum crossing altitudes that must 

be adhered to prior to passing the fix. 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. 

NOTE

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“Practical” or “feasible” may exist in some existing departure text instead of “practicable.” 

2. 

ODPs, SIDs, and DVAs assume normal aircraft performance, and that all engines are operating. 

Development of contingency procedures, required to cover the case of an engine failure or other emergency in 

flight that may occur after liftoff, is the responsibility of the operator. (More detailed information on this subject 

is available in Advisory Circular AC 120

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91, Airport Obstacle Analysis, and in the “Departure Procedures” 

section of chapter 2 in the Instrument Procedures Handbook, FAA

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H

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8083

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16.) 

3. 

The 40:1 obstacle identification surface (OIS) begins at the departure end of runway (DER) and slopes 

upward at 152 FPNM until reaching the minimum IFR altitude or entering the en route structure. This assessment 

area is limited to 25 NM from the airport in nonmountainous areas and 46 NM in designated mountainous areas. 

Beyond this distance, the pilot is responsible for obstacle clearance if not operating on a published route, if below 

(having not reached) the MEA or MOCA of a published route, or an ATC assigned altitude. See FIG 5

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2

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1. (Ref 

14 CFR 91.177 for further information on en route altitudes.) 

NOTE

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ODPs are normally designed to terminate within these distance limitations, however, some ODPs will contain routes that 

may exceed 25/46 NM; these routes will ensure obstacle protection until reaching the end of the ODP. 

4. 

Obstacles that are located within 1 NM of the DER and penetrate the 40:1 OCS are referred to as “low, 

close

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in obstacles.” The standard required obstacle clearance (ROC) of 48 feet per NM to clear these obstacles 

would require a climb gradient greater than 200 feet per NM for a very short distance, only until the aircraft was 

200 feet above the DER. To eliminate publishing an excessive climb gradient, the obstacle AGL/MSL height and 

location relative to the DER is noted in the “Take

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off Minimums and (OBSTACLE) Departure Procedures” 

section of a given Terminal Procedures Publication (TPP) booklet. 

(a) 

Pilots must refer to the TPP booklet  or the Graphic ODP for information on these obstacles. These 

obstacle notes will no longer be published on SIDs. Pilots assigned a SID for departure must refer to the airport 

entry in the TPP to obtain information on these obstacles. 

(b) 

The purpose of noting obstacles in the “Take

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off Minimums and (OBSTACLE) Departure 

Procedures” section of the TPP is to identify the obstacle(s) and alert the pilot to the height and location of the 

obstacle(s) so they can be avoided. This can be accomplished in a variety of ways; for example, the pilot may 

be able to see the obstruction and maneuver around the obstacle(s) if necessary; early liftoff/climb performance 

may allow the aircraft to cross well above the obstacle(s); or if the obstacle(s) cannot be visually acquired during 

departure, preflight planning should take into account what turns or other maneuvers may be necessary 

immediately after takeoff to avoid the obstruction(s). 

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2

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8 

Departure Procedures