Reply To: Approach/Landing Climb – Inflight Icing Penalty
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:
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.