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6 Answers

IFR departure

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Instrument Rating

When does the takeoff techically end, is it at 1500 ft AGL after which the en route segment begins? 

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6 Answers



  1. John D Collins on May 26, 2014

    I am not quite sure what you are getting at, but 91.177 prescribes minimum IFR altitudes except for takeoff and landing. So in that context, takeoff includes the climb to the Minimum IFR altitude at which point 91.177 is applicable.

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  2. Mark Kolber on May 26, 2014

    Equally clueless as to what you mean. Perhaps you are referring to the point at which IFR obstruction clearance begins and you may safely turn on course (assuming no special takeoff minimums or procedures), 400′ agl?

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  3. Wes Beard on May 26, 2014

    I think you are thinking about first segment, second segment, the transition segment and the final segment.

    These four segments are used in calculating takeoff performance up to 1500. This number has nothing to do with a standard takeoff (all engines operating) or a TERPS departure procedure.

    First segment begins when the aircraft takeoffs and ends with gear retraction. The airplane must have a positive rate of climb.

    Second segment ends at 400′ AGL (some manufacturers will make this segment end at 1500′ AGL and not worry about the final two segments). The airplane must be able to climb at 2.4% climb gradient.

    The transition segment is a level altitude segment designed to increase airspeed up to the single engine climb speed. Flaps are retracted on schedule.

    The final segment begins when the airplane reaches its single engine climb speed and ends at 1500′ AGL.

    If you were to look in the Part 25 certified AFM, you will need to calculate your max weight given the fact that you must maintain those minimum climb gradients listed above. Most AFM’s do this work for you and give you a takeoff weight limit chart.

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  4. Mike Urban on May 26, 2014

    Thank you all and sorry for not being clear in my question. I will rephrase.

    My question is about the standard climb gradient required for IFR departure; when does this requirement ends? i.e. can I climb at 200 fpnm upto certain distance or altitude then climb at the min en route climb gradient (up to 5000′ 150’/NM, between 5000′ to 10,000′ 120’/NM, above 10,000′ 100’/NM).

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  5. Wes Beard on May 27, 2014

    The climb gradient guarantees obstacle clearance on a 152 FT:1 NM scale out to 25 NM in non-mountainous terrain or 46 NM in mountainous terrain.

    If the MEA for the route is met on the climb gradient before 25 or 46 NM from the runway then you are in the enroute structure.

    Reference AIM 5-2-8.

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  6. Mike Urban on May 27, 2014

    Thank you much Wes,

    I made more search and I found the following:

    1. The 40:1 obstacle identification surface (OIS) begins at the departure end of runway
    (DER) and slopes upward at 152’/nm until reaching the min IFR altitude or
    entering the en route structure.

    2. The above assessment area is limited to 25 NM from the airport in non-mountainous areas and 46 NM in designated mountainous areas.

    3. IF YOU ARE UNABLE TO ENTER THE EN-ROUTE STRUCTURE BEYOND THESE DISTANCES, YOU ARE RESPONSIBLE FOR OBSTACLE CLEARANCE UNTIL REACHING THE EN-ROUTE STRUCTURE at or above the MEA/MOCA or an ATC assigned altitude.

    NOTE: Some ODPs provide obstacle clearance all the way to the en-route structure exceeding the typical assessment area distances (the 25 nm & 46 nm). That means, as long as you maintain climbing at 200’/nm to the en-route structure, you won’t worry about obstacle clearance.

    Reference: http://www.ce560xl.com/files/Departure_Procedures.pdf SEE PAGE 8

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