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Aviation History
1957
1957 - 0412.PDF
MM3 414 FLIGHT, 29 March 1957 "Flight" photographs "NIGHT PHOTO JET' 39,686 lb empty and has gross and overload weights of 70,000 lband 79,000 lb respectively. Though the aircraft may land at its gross weight, the touch-down speed in this condition would be as high as 160 kt. This is, of course, a quite abnormal case and the approach is usuallymade at 150 kt, leading to a touchdown at 115 kt. The combina- tion of drag-chute, high-lift flaps, air-brakes and powerful discwheel-brakes pull it up in quite a short space. The narrow- track main undercarriage seems to present surprisingly few prob-lems. There is a slight, but not excessive, tendency to roll on the ground, but hydraulic nosewheel steering gives very good control.Steering is operated by the rudder pedals, a three-position switch allowing selection of "nosewheel free," "taxi" or "take-off"settings. In the take-off condition full rudder-pedal travel gives only ten degrees' deflection of the nosewheel. In cross-windsthere is a distinct tendency to "bicycle," which means lifting one main wheel off the ground, but this is quite simply overcomeby applying full opposite aileron. Each aileron is in two sections and a spoiler immediately ahead of the outboard flap section ismechanically interlinked with the ailerons on each side. The spoiler rises in direct angular relationship to the aileron itselfand has its own hydraulic booster. To cure pitch-up troubles which initially arose, and to givegood low-speed handling, the leading edge outboard of the engine pylons is fitted with aerodynamically operated slats in threesections. The outboard section on each side ope .is progressively in turns at speeds below 300 kt and all slats are fully extendedat about 180 kts. All control surfaces are hydraulically boosted at a ratio of25 :1, and the tailplane incidence is changed by two electric jacks working together. The hydraulic power supply is duplicated,but neither pipes nor jacks have a stand-by. In case of malfunc- tion, therefore, hydraulic boost is manually disconnected, butcannot be re-established in flight. Though stick loads are there- after very high, the aircraft can be landed without difficulty.There are, in fact, two hydraulic pumps on each engine, one of each pair being regarded as a stand-by, but only a single pres-sure reservoir. The whole hydraulic system is divided into five circuits—"utility," serving undercarriage, brakes, nosewheelsteering, airbrakes and flaps; "main emergency," providing photoflash release, undercarriage and airbrake standby; "aileronboost"; "rudder/elevator boost"; and the "alternate emergency," by which power from the boost circuits can be interconnectedto the utility services. The Douglas representative claimed absolute reliability for theaircraft systems; and the U.S.A.F. did indeed carry out a long test programme to establish this. The RB-66B's electrical system,by General Electric, is supplied by a 28 V D.C. generator and a 115 V, 400 c/s three-phase alternator at each engine. For allgeneral services A.C and D.C. are used in parallel, a particular example being the tailplane incidence-change. In this case bothA.C. and D.C. jacks work together, the A.C. jack acting as a brake to the D.C. unit. With the former disconnected the tailplane canbe freely moved by hand on the ground. But the A.C. jack gives five-times-faster tailplane incidence change. In two-and-a-halfyears of intensive testing no case of runaway has occurred. The RB-66's crew compartment differs completely from that ofits Naval A3D counterpart. Particularly impressive is the AiResearch air-conditioning system which uses a combination ofcompressor-bled and ram air and can reduce cabin temperature to The 420th Air Refueling Squadron's KB-50 three-point probe-ond- drogue tankers were converted by Hayes Aircraft Corporation. One reel unit replaces the tail turret and the other two are in pods outboard of the 500 U.S.-gal undenting tanks. as little as 45 deg F while the aircraft is flying "flat out on thedeck." There are both water separators and a humidity control, and cabin temperature can be preselected by die pilot. TheAmericans described the degrees of snow and ice which the system could on occasion produce. Pressurization settings are 5 lb/sq innormally, and 2.75 lb/sq in for combat. The liquid-oxygen installation can provide pressure breathing; but this is notnormally required, as the B-66 does not fly high enough. In addition, compressor-bled air is used for de-icing and anti-icing ofthe whole wing leading edge, tailplane and fin leading edges, engine pylons, nacelle forward sections and the main noseradome. With the system switched on die RB-66B can take off at full load, but it takes a little longer to get off the ground. Enginestarting is by compressed air supplied from a small gas turbine in a ground trolley. The large drag-parachute is deployed on every landing andthough the aircraft can safely taxi with it attached, the chute is normally dropped at a designated pick-up point at the end of therunway to avoid unnecessary wear and tear. There are twelve attachment points for J.A.T.O. bottles on the aft fuselage flanks,but this assistance is for use only when the aircraft has landed on an airfield it cannot get out of again. The American pilots didnot think that they could ever safely land on an airfield small enough to require assisted take-off. The RB-66B is fitted with a Minneapolis-Honeywell autopilotwhich has a height and heading lock facility and normal knob control. It is not tied in with the camera installation, but can becoupled with I.L.S. for automatic approaches. At the moment the autopilot is little used, for flights are still fairly short, but theRB-66B has a marked panel on the right-hand side of the nose cone which indicates that an air refuelling probe may be fittedthere. One of the aircraft at Sculthorpe actually carried the probe, and when this facility comes into general use for longflights the autopilot will come into its own. With the RB-66Bs at Sculthorpe is the 420th Air RefuelingSqn., T.A.C., which has a mixed bag of KB-29 boom refuellers (for F-84Fs) and KB-50 three-hose probe-and-drogue refuellers.The probe-and-drogue aircraft were busily flying during our visit but we could see no receivers other than the RB-66s. It isunlikely, however, that more man two 66s would be able to contact the tanker at a time. As for maintenance, the RB-66B appears already to be buildingup a fine record. The Douglas/U.S.A.F. reliability programme is paying off, and the Allison J71 10,000 lb thrust engines offerexcellent accessibility. The complete underside cowling of each J71 pod hinges open and an engine can be changed in about fivehours, although the job has been done very much more quickly. The J71 has a very large main rotating assembly with no fewerthan sixteen compressor stages, but it is provided with an accelera- tion control which will take it from idling to maximum poweralmost as fast as the power lever can be moved. In the cockpit the pilot sits hard over to the left and holds the power levers inhis right hand. The airbrake switch is incorporated in one of them and the braking parachute release lever is close by. Altogether the RB-66B is well liked by its crews and the con-version programme is going well. The 19th Sqn. in any case should have no great difficulty with it since they have on fouroccasions won the U.S.A.F.E. tactical squadron proficiency award. Though the U.S.A.F. originally hoped to buy the Naval A3DSkywarrior off-the-shelf with only six alterations, they ended up with over 400, including a two-degree change in wing incidenceand a complete new fuselage layout. Add to this the B-66B bomber, RB-66B photographic and RB-66C radio reconnaissanceversions, all radically different, and the B-66 became a full-scale development project. The result in terms of a series of weaponsmay or may not be considered worth many years of effort by the Douglas Long Beach Division and U.S.A.F. C.M.L. Drag-chute, flaps and air-brakes are all extended for normal landings. Starboard aileron and spoiler are here raised to counteract roll caused by cross-wind and narrow-track undercarriage. The drag-chute is housed inside the tail-barbette access hatch under the fuselage.
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