Question on Helicopter Impact on Ground
Posted: Tue Jun 17, 2014 11:21 am
Q: Posted to INCR, "I've been asked to calculate/estimate the forward speed of a helicopter on impact with the ground. Briefly, it landed with forward airspeed on its
skids and slid for 9.6 metres then rolled due to a drop off in the terrain. has anyone derived a drag factor?
A: We normally don't cover helicopter crashes, however the following may be of assistance/use:
A 1987 research study we did with Calspan includes discussions of drag forces in various soils and can be found at:
One of the references in those reports:
(i.e. one would assume that plowing forces associated with 5 MPH and 50 MPH under similar conditions of sinkage, etc would be different)
See the full Calspan report for addition references (Bekker, Schuring, etc) related to motion resistance of soils.
skids and slid for 9.6 metres then rolled due to a drop off in the terrain. has anyone derived a drag factor?
A: We normally don't cover helicopter crashes, however the following may be of assistance/use:
A 1987 research study we did with Calspan includes discussions of drag forces in various soils and can be found at:
- Rollover Potential of Vehicles on Embankments, Sideslopes and other Roadside Features" (6 megs), Deleys, N. J., Parada, L.O, FHWA/RD-86/164, PB87-212783, August 1986
- Executive Summary Report
One of the references in those reports:
- Avery, JP Larson, S "Analysis of Army Fixed-Wing Cargo Restraint Design Criteria" USAAVLABS Technical report 67-3 PB#651219, Jan 1967
- FT = f*FN + v*AS*Xdot
- FT = resultant tangential force, lbs
F = nominal friction coeffcient
FN = normal load, lbs
V = viscous damping term, lb-sec/ft**3 (soil shear strength)
Xdot = velocity ft/sec
AS = total contact area, f**2
(i.e. one would assume that plowing forces associated with 5 MPH and 50 MPH under similar conditions of sinkage, etc would be different)
See the full Calspan report for addition references (Bekker, Schuring, etc) related to motion resistance of soils.