In recent years, considerable work has been done to evaluate the use of simple corrosion sensors to track corrosion in field environments and more recently on operational aircraft.  Prior to the work that is the subject of this paper, a study was done in a variety of ground environments  to evaluate effects on corrosion of wash intervals between 1 and 28 days.  These data have been reported at earlier conferences indicated that in severe environments there was a beneficial effect of very frequent washing (1-4 days).  However, at longer intervals there was almost no difference between not washing and any wash interval > about 4 days.  Since no base is likely to wash at these very short intervals this work provided some basis for aircraft wash extensions if the same effects could be demonstrated on operational aircraft.

The same corrosion sensors were installed in large numbers for this purpose on two MDS aircraft.  These were the C130 and H60 at multiple bases.  The C130 installations had 30+ sensors per aircraft as part of a larger study but only a few of the locations were regarded as relevant to wash effects.  These were 1) Landing Gear/wheelwells, 2) Sloping Longerons (FS737), 3) Air Deflector Door, and 4) Flapwells (various wing stations).  The H60 installations were unique and represented the first placement on outer skin at Left and Right sides, Belly, and in some cases Top, overhead cockpit.

The C130 base was documented as a moderate ESI with a normal 120 day wash interval. Half of the fleet of 8 aircraft remained at 120 days; half were extended to an ISO wash only of about 1 year.

The H60 base was coastal, severe, and had a normal interval of 30 days.  A similar strategy was adopted with half of the fleet extended to about 180 days.  In both cases, sensors were read about every 3 months.

This work is ongoing but 2+ years of data have now been accumulated.  The results so far are in good agreement with the ground based results and show no effects of wash interval at either base/ESI.  Possible reasons for these results will be discussed.  The possible implications from these results if applied fleetwide are very large cost reductions.  For the C130 fleet one estimate shows and increased airlift capacity equivalent to 2-3 additional aircraft.