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Honeywell Releases Improved #4 Carbon Seal To Address Bi-Modality And Risk Of AFT Sump Failure On The HTF7000 Series Engines

April 2021

Honeywell issued Service Bulletin AS907-72-9094 that calls for the replacement of the #4 carbon seal on the HTF7000/AS907 series engines. This SB is an improved #4 carbon seal and impacts the following aircraft.



AS907-1-1A Challenger 300


Challenger 350


Gulfstream 280


Textron Aviation Model 700 (Cessna Citation Longitude)


Embraer Legacy 450 Embraer Legacy 500

This new improved seal, PN 70041289-2, should be replaced at next access or cause.

Once SB AS907-72-9094 has been completed,

  • the 150-250 hour soap required by SB 72-9084 is no longer required, with the oil filter analysis intervals returning to the normal intervals per the applicable LMM.
  • the EEI download interval of every 25 – 35 days returns to the normal interval as well.
  • SB 72-9090 is no longer needed   

Other SBs required with SB AS907-72-9094:

  • 72-9080: Install new #4 bearing, PN 3035647-7
  • 72-9045: Install improved tower shaft bearing, PN 3033024-2, -4 or -6

For more information about this and other Honeywell Service Bulletins, don’t hesitate to contact me.