Approach/Landing Climb – Inflight Icing Penalty

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  • #449
    Chet Collett
    Participant

    All,

    I would like to ask how your dispatchers determine when to apply the Inflight Icing Penalty to the Landing Climb /Approach Climb Limit weights. What is the trigger? Is it based on anticipated inflight structural icing conditions, or is it based a flight segment where the “TAT inflight, is 10 degrees C (50 degrees F) or below and visible moisture in any form is present”?

    Either way, this penalty would not be required if the landing airport is warm
    (10 degrees C for the 737NG and 8 degrees C for the 737-400) because the AFM recognizes that the airframe ice will melt off when the temperature is warm prior to attempting a go-around.

    Clearly there are flights when there is no inflight structural icing anticipated, but the use of engine anti-ice may be required.

    Thanks,

    Chet Collett
    Director, Flight Operations Engineering
    Alaska Airlines
    206-392-6024
    303-246-0386 Cell

    #456
    Mike Byham
    Moderator

    Chet – below is what we have in our Flight Ops Manual (FOM) on dispatching into known icing conditions. Our (US Airways) Dispatcher Ops Manual refers to the FOM on this subject. It appears that although we supply the data we do not provide specific guidance for its use. Hope this helps.

    Mike Byham

    12.3.3 Dispatch into Known Icing Conditions
    A. No aircraft will be dispatched through known or forecast severe icing
    conditions. Aircraft may be dispatched through other known or
    forecast icing conditions if requirements of the MEL are met.
    B. Captains and Dispatchers must recognize the limitations of antiicing
    equipment in moderate or severe icing conditions. It is used
    as an aid in descending or ascending through icing conditions. No
    aircraft will be dispatched, continue to operate enroute or land
    when, in the opinion of the Captain or Dispatcher, icing conditions
    are expected that might adversely affect safety.
    C. Takeoffs will not be made when frost, snow or ice is adhering to the
    wings or control surfaces of the aircraft. (14 CFR 121.629)
    D. Condensation frost, caused by super-cooled fuel, is permitted on the
    lower wing surface between the front and rear spars (bottom of fuel
    tank area), if the fuselage and all other control surfaces of any kind
    are free of contamination. If deicing is required on any other aircraft
    surface, the under wing condensation frost will also be removed.
    E. In those cases where there is some question as to the necessity of
    deicing the aircraft before takeoff, the Captain’s decision will be
    final.

    #459
    Chet Collett
    Participant

    Let me try again and see if I can clarify my issue:

    The Boeing AFM uses the terminology of “possible ice accumulation” when it talks about the need to apply the Inflight Icing Correction to the Landing and Approach Climb Limit Weights. It seems clear that the intent of this correction is associated with structural icing conditions. Unfortunately, in the same paragraph Boeing uses the generic term of “icing conditions” which is defined later in Chapter 4 as it relates to when engine anti-ice should be used.

    Section 4 Page 3:
    7. Aircraft performance adjusted for possible ice accumulations is provided for planning flights into known or anticipated icing conditions.

    Climb Performance: Performance for en route climb, approach
    climb and landing climb accounting for possible ice accumulation
    is provided in AFM-DPI by selecting “Inflight Icing”. Use the
    en route “Inflight Icing” performance when operating in icing
    conditions during any part of the flight. Use the approach
    climb and landing climb “Inflight Icing” performance when
    operating in icing conditions during any part of the flight and
    the forecast landing temperature is below 10 degrees C.

    =====

    Section 4 Page 7:
    D E F I N I T I O N S (Continued)

    ICING CONDITIONS
    Icing conditions exist when the OAT on the ground and for takeoff, or TAT inflight, is 10 degrees C (50 degrees F) or below and visible moisture in any form is present (such as clouds, fog with visibility of one mile or less, rain, snow, sleet and ice crystals).

    Icing conditions also exist when the OAT on the ground and for
    takeoff is 10 degrees C (50 degrees F) or below when operating on ramps, taxiways or runways where surface snow, ice, standing water or slush may be ingested by the engines or freeze on engines, nacelles or engine sensor probes.

    We are convinced that it is safe and appropriate to clarify our guidance to the dispatchers that they should only apply this Inflight Icing Penalty when the flight is planned through anticipated structural icing conditions and the forecast landing OAT <10 degrees C (< 8 degrees C for the 737-400).

    Unfortunately, our Compliance Department is concerned that our FAA may interpret the AFMs use of the generic term “icing conditions” in “operating in icing conditions during any part of the flight” as “TAT inflight, is 10 degrees C (50 degrees F) or below and visible moisture in any form is present (such as clouds, fog with visibility of one mile or less, rain, snow, sleet and ice crystals)” rather than “structural icing conditions”

    As a result, we have Dispatchers applying this Inflight Icing Correction when it is raining and 8 degrees C at the departure station (NO Structural Icing is anticipated anywhere along the route of flight) and the arrival forecast temp is colder than 10 degrees C.

    Hence why I asked what I thought was the simple question:

    What is your trigger for applying the Inflight Icing Correction? Is it based on anticipated inflight structural icing conditions, or is it based a flight segment where the “TAT inflight, is 10 degrees C (50 degrees F) or below and visible moisture in any form is present”?

    Thanks for your responces,

    Chet Collett
    Director, Flight Operations Engineering
    Alaska Airlines
    206-392-6024
    303-246-0386 Cell

    #474
    John Arne Lande
    Participant

    Hi Chet!

    For what it’s worth (we operate in Europa under EASA), we use anticipated inflight structural icing conditions in our company. Enroute, the pilots use the WTAI switch as a trigger to include the penalty in their landing calculation or not. If they have used WTAI (during any part of the flighrt), thay have picked up ice both on wing and tail, hence the penalty (if the temperature is below 10/8 deg etc.).

    We operate 737-800 and 737-300. We experience that this is rearly limiting, but it might happen when we have increased missed approach gradients combined with the use of Engine Anti Ice. The cure is to plan with a “no bleed” landing.

    My 5 cents;-)

    John Lande
    Captain – Manager Performance
    Norwegian Air

    #539
    Don Stimson
    Participant

    Hi Chet,
    I think your concern over how the FAA may interpret the application of the approach/landing climb icing penalties is well founded. The basic philosophy has been that if the airplane has encountered icing conditions at any time during the flight, unless there is a means to determine that there is no airframe ice accretion present at the time of landing, the icing penalties should be applied. This is fairly consistent with John Lande’s comments above and is consistent with the use of a speed additive for a flaps 15 landing if WTAI was used at any time during the flight.

    The means for determining whether or not any ice accretion exists at the time of landing for an earlier icing encounter is not cut and dried. For example, if I flew in icing conditions for ten minutes two hours ago and have been in warm tropical air for the last hour, must I still account for possible ice accretions? There isn’t any
    “formula” to answer that I know of to answer that question.

    Don Stimson
    former FAA certification specialist

    #845
    Chet Collett
    Participant

    I was able to get Boeing to agree (in writing) that the In Flight Icing Penalty does not apply if only engine anti-ice would be required during the flight. The words that I used for the positive Boeing response were:

    We believe that “ice accumulation” as it is referred to in (AFM) paragraph 7 section 4 Page 3 is tied to the “structural icing conditions”, and not the distinct “icing conditions” associated with engines anti-ice usage. Our dispatchers have the tools to determine when inflight structural icing is to be anticipated, and they flight plan accordingly. This is a distinctly different function from them determining if Engine Anti-ice will be required for either takeoff or landing.

    We are not asking Boeing to change any of the wording in the AFM (although it would be nice if this were clarified in the 737MAX AFM). We are simply asking for a NTO to our interpretation as to when this Inflight Icing correction needs to be applied to the landing/approach climb limit weights. We believe the following statement is accurate and correct, and follows the intent of the AFM Landing Climb and Approach Climb Limit correction guidelines:

    The use of engine anti-ice (alone) should not be the trigger for when the Inflight Icing correction needs to be applied. The Inflight Icing correction is intended to protect climb performance for landing from the effects of ice accumulation on the unheated surfaces. If there are no known or anticipated structural icing conditions along the planned route of flight, the “Inflight Icing” penalty does not need to be applied.

    Here is how we will display these adjustments to our Pilots and Dispatchers:

    The In Flight Icing adjustment is intended to ensure the aircraft meets the required AFM go-around performance (Climb Limit), assuming the unheated surfaces of the airframe are laden with an extreme accumulation of ice.

    This penalty should be applied by the Dispatcher during the pre-flight planning process if the flight is anticipated to encounter structural icing conditions and the OAT at the landing airport is forecast to be:
    • less than 10°C for 737NG or
    • less than 8°C for 737-400

    The use of engine anti-ice (alone) should not be the trigger for when the Inflight Icing correction needs to be applied. If there are no known or anticipated structural icing conditions along the planned route of flight, the “In Flight Icing” penalty does not need to be applied.

    Here is Boeing’s response:

    RESPONSE:

    Boeing has reviewed the attached proposal of the Alaska Airlines interpretation and application of the Approach Climb/Landing Climb Limit Inflight Icing correction, and we consider it equivalent to Boeing’s.

    Boeing also notes that with this request, Alaska Airlines is not asking for a variance from a Boeing flight crew procedure or a modified airplane repair. These types of requests would be appropriate for the use of a Boeing No Technical Objection (NTO) statement. However, we understand this request to be a confirmation that your interpretation and application of the inflight icing adjustments is as intended.

    The attached multi-model Service Letter (SL) defines what an NTO is and how it is associated with data or changes to Boeing publications that an operator would like to accomplish:

    No Technical Objection, No Objection, or Technical Concurrence:
    Any of these responses may be used when a repair, installation, modification, or procedure has been proposed by an operator or MRO, and Boeing has completed a limited review, and no obvious problems have been found. This review is intended to determine if there are any obvious technical, operational, procedural, and/or interference issues with the proposal, based on the information/data provided.

    Boeing agrees with Alaska Airlines that your interpretation and application of the Approach Climb/Landing Climb Limit Inflight Icing correction is correct.

    We trust this information is helpful. Please let us know if you have additional questions or concerns.

    Best Regards,

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