TM No. 327 



DROGUE DESIGN AND PAYOUT 



Figure 2 shovs the design of the drog^je system. All drogues were identical 

 in construction. The parachute drogue presented a drag area of about k'^ 

 square meters to the current at depths vhere measurements vere taken. This 

 vas in contrast to a drag area of about three square meters vhere the styro- 

 foam float was exposed to surface water and wind. 



After the surface float was launched, the specified amount of wire was 

 payed out through an indicating meter wheel while the vessel steamed slowly 

 upwind. When the proper amount of wire was payed out, a cheek clamp was 

 attached to the suspension wire. The parachute and a 50-pound weight were 

 secured to the cheek clamp, and the suspension wire was cut. The weight was 

 then lowered over the side until the parachute shrouds carried the full weight. 

 At this time the weight was released and the parachute was pulled downward by 

 the weight. (The parachute is payed out exactly opposite to payout in the 

 airj i.e,, the shrouds are payed out first, the canopy being the last part to 

 enter the water.) In all cases, it was possible to see the parachute open 

 under water. 



NAVIGATION AND TEIACKING 



The positions of the surface floats relative to known landmarks were 

 detennined with a Decca Hi -Fix System (Decca Navigator Company, Ltd., London), 

 and an auxiliary fix was taken with navigation radar. 



The Decca Hi-Fix is a high precision, lightweight, electronic position- 

 fixing system, intended primarily for use at short ranges. The system is 

 designed for hydrographic, geophysical, andcother surveys in which an accuracy 

 of less than one meter is required, and which demand the use of an electronic 

 surveying system that is readily portable, siiaple to operate, and quick to 

 install. Decca Hi-Flx receivers were temporarily installed on both vessels, 

 and were used independently but in conjunction with the radars. 



The E.J.W. FAY was equipped with a Decca kOk navigation radar, which is 

 specified to have a frequency of 9320=9if80 rac/sec and a display discrimina- 

 tion of 20 yards. Range scales in nautical miles are 0.75, 1.5, 3, 6, 12, 

 2k, USo On shorter range scales, the range ring accuracy is 1 l/2 percent of 

 the maximum of the range used or 75 yards, whichever is the greater. The 

 variable range marker accuracy is better than 1 percent of the range ring 

 accuracy. The bearing resolution is ±1°. The OCEAN PEARL was equipped with 

 a Decca 303 navigation radar, which has characteristics similar to the Decca 

 kOk, The ranges most used were 6, 12, and 2k nautical miles. 



The Decca Hi-Flx "net" in the Tongue of the Ocean, shown on figure 1, 

 consists of three land-based transmitting stations (two slave stations in 

 conjunction with the common master station). Typical operating distances 



