VTOL DOWNWASH IMPINGEMENT STUDY SURFACE EROSION TESTS
Abstract
A mobile test rig, mounting a two-foot-ducted propeller, capable of providing disk loadings up to 145 lbs/sq ft, was used to provide a cold air jet. This jet was allowed to impinge upon surfaces which might be considered unprepared landing sites. The range of duct exit height above the surface was from one-half to three diameters, and thrust angle inclinations of 0, 30 and 60 deg. Surfaces with light vegetation or hard-packed soil surfaces show little erosion (over) from disk loadings to 145 lbs/sq ft. The hardpacked surfaces normally have fine loose dust on top, which produces a large dust cloud even at very low disk loadings. In general the loose material surfaces erode rapidly, and large holes are formed in a short time. The gravel, with a mean particle size of about seven mm and large particles to forty mm, was eroded at a rate of 150 lbs/sec at a disk loading of 145 lbs/sq ft. Wet sand showed minor erosion under the same test conditions. Over water the surface spray started at disk loadings between eight and fifteen lbs/sq ft. Between the disk loadings of thirty to sixty lbs/sq ft the spray pattern changes from a radial surface spray to one in which there is considerable vertical motion and ingestion into the duct inlet.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1960
- Accession Number
- AD0248356
Entities
People
- A. Stephen Morse
- H. Newhouse