From the Flight Deck: Divine Lines

From the Flight Deck: Divine Lines

Pilot commandments & engine-out SIDs

“It ain’t those parts of the Bible that I can’t understand that bother me, it’s the parts that I do understand.”
– Mark Twain

Wouldn’t it be nice to have a GPS course for navigating smoothly around life’s obstacles? The database would contain all societal parameters, personal interaction norms and behavioral boundaries. The control panel would have an icon for our career, finances, health, relationships and our family. A “Thou Shalt Not” limiter would monitor all the pesky rules that prevent us from saying and doing whatever we want.

More than 2.2 billion folks believe that there is just such a thing. The operating manual is a book-of-books that is the most read and studied text in the history of human communication. While the course it describes may be a divine guide to our destiny, it does not promise that the ride will be safe or smooth, that it will avoid obstacles, or that it will be direct. The manual can be cryptic, vague, circuitous and harrowing. And even with prayer, its path doesn’t always lead to the destination we planned.

We don’t like cryptic, vague, circuitous or harrowing when flying our airplanes. And we certainly don’t want to end up somewhere other than where we planned. So, we’re less theological in our dead-reckoning and pilotage techniques; primarily focused on navigating to our destination rather than to our destiny. No biblical metaphors to interpret. We verify and re-verify that the points to which we are navigating are correct — a course that is safe and efficient. In the Part 121 world, we call it The Magenta Line.

However, the ability to fly a circuitous route using GPS systems can be useful. A circuitous course can be used to avoid special use airspace, undesirable winds and weather or to fly a track that is free of obstacles if we are performance limited; such as when an engine fails after V1. If a straight-ahead departure is not possible, we need a heavenly plan, a lifesaving path to follow. We need an EOSID (Engine Out SID).

A Procedural Rabbit

An engine failure during takeoff is an emergency and therefore takes precedence over noise abatement, other traffic, SIDs, ODPs (Obstacle Departure Plan), and other normal operating considerations. This implies that you are not required to maintain the SID or ODP profile, either laterally or vertically, thus waiving some of those pesky “Thou Shalt Not’s.”

In the event of a deviation from the cleared routing, however, the PIC should advise ATC as soon as possible by telling them that you have an emergency and are flying an engine-out procedure, an emergency turn or an escape routing. The terms are interchangeable so don’t get hung up on the verbiage. Unless developed by the local airport, though, ATC will not know the specifics of the procedure, but they will understand your intent and clear traffic when necessary. Even so, once airborne is not the time to wing it and pull a procedural rabbit-out-of-your-engine-failure hat.

Planning for the failure before takeoff is required. After an engine failure, high terrain, man-made obstacles, the airport elevation, aircraft performance or any combination of these factors may make it impossible to meet the climb gradient described in a SID or an ODP, whereas EOSIDs are based on specific aircraft performance in case of an engine failure. It’s the responsibility of the operator to recognize this performance deficit and to develop engine-out takeoff procedures when and where required. In such cases, EOSIDs should have sufficient guidance, both to avoid obstructions and so that they can be followed in IMC and VMC.

The Nitty Gritty

Pilots departing an airport under IFR and operating under Part 121 or 135 are required by the FAR’s to use an OEI procedure that assures compliance with obstacle clearance requirements.

According to Advisory Circular 120-91:

“The methods and guidelines presented in this AC are neither mandatory nor the only acceptable methods for ensuring compliance with the regulatory sections. Operators may use other methods if those methods are shown to provide the necessary level of safety and are acceptable to the FAA.”

OEI procedures developed by Part 121 and 135 operators follow these guidelines and are then “accepted” by their company’s FAA POI (Principal Operations Inspector). Airport and runway analysis involves complex, usually computerized computations of aircraft performance and the use of extensive obstacle databases and terrain information. Methods of complying include either using a contract company to create avoidance procedures or developing your own. Most Part 121 operators have performance engineers on staff to conduct runway analysis and produce Emergency Turn data for their company. Part 135 operators often use third-party vendors to generate the desired information. And, in some cases, EOSIDs are published by individual airports.

The most widely used OEI planning method compares a climb gradient published on a SID or ODP with the OEI climb gradient from the Aircraft Flight Manual (AFM); usually the second segment OEI climb gradient. The maximum allowable bank angle below 400 feet AGL is typically 15 degrees and any maneuvers should guide the aircraft around or away from terrain using this bank angle constraint.

Other considerations in planning include ground based navaid and GPS tolerances, obstacle clearance during straight takeoff and turns, wind effect during turns and loss of climb performance during turns. Any procedures must also be designed to ensure that the third segment climb (level acceleration/flap retraction) can be completed and thrust reduced to maximum continuous (MCT) before the time limit for takeoff thrust. Ultimately, the path of the EOSID should lead to a point at which the aircraft can plan a landing or continue to the destination or an alternate.

“I have wondered at times what the Ten Commandments would have looked like if Moses had run them through the U.S. Congress.”

– Ronald Reagan

According to AC 120-91, Part 91 operators can develop EOSIDs on their own — no need to run them through the U.S. Congress. The engineering required to “build” the procedure on paper, however, is daunting. Since flying an actual engine-out departure is harrowing, individual operators should accomplish EOSID construction in a simulator. With an engine failure at V1, a warm OAT and at gross weight, use the “mark” function of either the simulator itself or the avionics in the cockpit to record fixes as you develop an escape route.

The points on an EOSID can simply be a series of GPS fixes, a radial DME fix using a navaid or an altitude based fix/turn. While most procedures do not use a ground-based navaid due to accuracy, reliability, difficulty in navigation and possible interference from the very obstructions you are trying to avoid, they will provide a plan that is better than no plan at all.

The first point on your EOSID should be straight ahead after takeoff to either a fix or an altitude. You would fly to this point while you retract the gear and get the airplane under control. The point should be far enough away to stabilize the aircraft but close enough to allow the first turn in time to avoid obstacles. Subsequent turn points should create a path that leads you to a safe holding pattern in which to climb further, or one that will guide you back to the airport. Once you have a series of fixes, you can save them as a flight plan in your FMS. Review and confirm the fixes as you would your normal route. Then, when ready for takeoff, have the EOSID standing by with immediate execution available. If the takeoff is normal, fly the ATC clearance, published SID or ODP. If an engine fails, select the EOSID, tell ATC you’re an emergency and fly the divine line.

Magenta Line Metaphors

Following the proper path can be a challenge in the air and in life. Especially if our journey is fraught with obstacles, “Thou Shalt Not’s” or one set of footprints in the sand. So, unless we want to reach our destiny before our destination, perhaps in a harrowing fashion, we shouldn’t wing it. Instead, follow reliable guidance.

The next time you’re in the sim, practice the EOSIDs you already have or develop new ones for the obstacle-challenged airports you use. It should be fun and could help you to avoid a kerfuffle. Because if you’re performance limited, you won’t have time to interpret a metaphor, invent an escape procedure or look up the definition of kerfuffle.

Happy Easter my friends. 

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