UNDERWAY REPLENISHMENT NWP 4-01.4 - Historic Naval Ships ...

NWP 4-01.410.2.1 VERTREP With Dissimilar Aircraft.VERTREP involving dissimilar types of aircraft (i.e.,one H-46 and one H-60) or dissimilar service aircraft (i.e.,USN H-46 and USMC H-46) is inherently more hazardousin that a VERTREP evolution is in many respects a typeof highly dynamic formation flight. Varying aircraft patternsand procedures lead to uncertainties and dangers inan evolution that depends on a smooth and predictablemovement of aircraft. Therefore, if dissimilar types of aircraftor dissimilar service aircraft are to be used during aVERTREP evolution, a face-to-face operational prebriefshould be conducted. Items to be briefed shall include,but not be limited to, VERTREP patterns, safety of flightitems, and emergency procedures.10.2.2 Factors Affecting VERTREP10.2.2.1 Wind. For VERTREP, the helicopter musthover over both the delivery and receiving ships. Moreengine power is required to fly at extremely low air speeds(0 to 15 knots) and high air speeds (90 knots and above)than is required at medium air speeds. The difference betweenengine power required to hover without a load andthe maximum engine power available is the excess powerwhich can be used to carry cargo. A relative wind of 15 to30 knots is considered ideal. The helicopter should takeoff, make approaches, and hover into the relative wind. Arelative wind of 330° or 030° is optimum for VERTREP.Other relative winds are acceptable under differingconditions. Under high wind conditions, sea state isusually severe enough to cause ships to pitch and rollexcessively when headed into the seas. If these conditionsexist, it is normally better to steam downsea toprovide a steadier deck. A downsea course probablywill be downwind, but the relative wind may still besuitable for VERTREP with the H-46, and cargo handlingconditions for the crews on the exposed deck willbe improved. However, the increased rotor downwashfrom the hovering helicopter — because of this downwindcondition — will create additional hazards for bothhelicopter and deck crews in the form of high winds,flying debris, and salt spray. The pilot should be consultedwhen a downwind course is contemplated.NotePilots conducting VERTREP operations shall benotified prior to any course change. VERTREPmay continue at the discretion of the aircraftcommander while the ship is in a turn.10.2.2.2 Ship Stationing. See Figure 10-1 for typicalship stations for VERTREP. Examples of otherVERTREP stations and situations are:1. A carrier is on a downwind course betweenflight operations.2. The receiving ship (for VERTREP) is approachinga control ship for CONREP.3. The receiving ship (for VERTREP) is alongsidea delivery ship for CONREP.4. Destroyers are in lifeguard station or proceedingto and from screening stations.5. The receiving ship is at anchor, lying-to offshore,or steaming offshore when involved incombat tasks.NoteFor night VERTREP the receiving ship shouldbe abeam at a distance of 300 to 500 yards.There will be times when VERTREP can be conductedwell beyond visual range, depending on the followingfactors:1. Adequate communications and navigation aidsbetween ships and helicopters2. Type and number of loads (internal and external)3. Time required and time available versus operationalpriority of requirement4. Whether aircraft NATOPS requirements fornight VERTREP can be met.Generally, the carrying of external loads for long distances— over 35 miles (56 km) for heavy, high densityloads and over 25 miles (40 km) for light, low densityloads — is not considered a standard VERTREP procedure,but rather a capability that should be reserved forhigh priority cargo that justifies the time involved.NoteA light, low density load is defined as anyload with a high drag-weight ratio: generally,any load weighing less than 500 lb (227kg) and those loads that have exceptionallylarge sail areas. Included in this definitionare such items as aircraft drop tanks or canopies,rotor blade containers, and empty missilecontainers, which have aerodynamiccharacteristics that require extremely slowair speeds for safe VERTREP transit.10-2 ORIGINAL