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separation between the obstacle clearance surface (OCS) and the required climb gradient of 200 ft/NM. The ROC value is zero at the DER elevation and increases along the departure route until the ROC value appropriate for en route flight is achieved. The appropriate ROC value for en route operations is typically achieved about 25 NM for 1,000 feet of ROC in non-mountainous areas, and 46 NM for 2,000 feet of ROC in mountainous areas. 

If taking off from a runway using a diverse departure (a runway without a published ODP), beyond these distances the pilot is responsible for obstacle clearance if not operating on a published route, and if below the MEA or MOCA of a published route, or below an ATC-assigned altitude. [Figure 1-15] 

Recent changes in TERPS criteria make the OCS lower and more restrictive. [Figure 1-16] However, there are many departures today that were evaluated under the old criteria that allowed some obstacle surfaces to be as high as 35 feet at the DER. [Figure 1-14] Since there is no way for the pilot to determine whether the departure was evaluated using the previous or current criteria, and until all departures have been evaluated using the current criteria, pilots need to be very familiar with the departure environment and associated obstacles, especially if crossing the DER at less than 35 feet. 

All departure procedures are initially assessed for obstacle clearance based on a 40:1 Obstacle Clearance Surface (OCS). If no obstacles penetrate this 40:1 OCS, the standard 200 ft/NM climb gradient provides a minimum of 48 ft/NM of clearance above objects that do not penetrate the slope. The departure design must also include the acquisition of positive course guidance (PCG), typically within 5 to 10 NM of the DER for straight departures. Even when aircraft performance greatly exceeds the minimum climb gradient, the published departure routing must always be flown. 

Airports publish the declared distances in the A/FD section of the CS. These include takeoff runway available (TORA), takeoff distance available (TODA), accelerate-stop distance available (ASDA), and landing distance available (LDA). These distances are calculated by adding to the full length of paved runway any applicable clearway or stop-way and subtracting from that sum the sections of the runway unsuitable for satisfying the required takeoff run, takeoff, accelerate/stop, or landing distance as shown in Figure 1-16. 

Optimally, the 40 to 1 slope would work for every departure design; however, due to terrain and manmade obstacles, it is often necessary to use alternative requirements to accomplish a safe, obstacle-free departure design. In such cases, the design of the departure may incorporate a 

climb gradient greater than 200 ft/NM, an increase in the standard takeoff minimums to allow the aircraft to “see and avoid” the obstacles, a standard climb of 200 ft/NM with a specified reduced takeoff length, or a combination of these options and a specific departure route. 

## If a departure route is specified, it must be flown in conjunction with the other options. 

The obstacle environment may require a climb gradient greater than 200 ft/NM. In these cases, the ROC provided above obstacles is equivalent to 24 percent of the published climb gradient. The required climb gradient, for obstacle purposes on ODPs and SIDs, is obtained by using the formulas: 

Standard Formula 

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O = obstacle mean sea level (MSL) elevation E = climb gradient starting MSL elevation D = distance (NM) from DER to the obstacle 

Examples: 

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Round to 352 ft/NM *Military only 

These formulas are published in FAA Order 8260.3 for calculating the required climb gradient to clear obstacles. 

The following formula is used for calculating SID climb gradients for other than obstacles (i.e., ATC requirements): 

<img src='content_image/518102.jpg'>

A = “climb to” altitude E = climb gradient starting MSL elevation D = distance (NM) from the beginning of the climb 

Example: 

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## Note: The climb gradient must be equal to or greater than the gradient required for obstacles along the route of flight. 

The published climb gradient, obstacle or otherwise, is 

Round to 316 ft/NM 

DoD Option* 

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