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Morrow Project SK-5 Specifications

Page history last edited by Michael 3 years, 10 months ago

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SK-5 in assault configuration

 

A. rudder lock bar; B, RDF and magnetic compasses; C, microphone; D, propulsion motor temperature gauge; E, reactor temperature gauge; F, start switch; G, lift motor temperature gauge; H, clock; I, Autonav repeater; J, propulsion tachometer and counter; K, lift tachometer and counter; L, propeller pitch indicator; M, air speed indicator; N, skirt lift control; O, intercom, loudspeaker, horn, siren and radio controls; P, landing jack controls; Q, elevator trim control; R, power and pitch control; S, rudder pedals.

 

 

     The Morrow Project's SK-5 hovercraft were built in Grand Bend, Ontario, at a Bell Aerospace factory.

 

interior plan of the assault version

 

Characteristics

 

     This  combat hovercraft is meant for employment on water, swamps or grassland; the hull will float in water even with the engines off. The SK-5 utilizes a flexible, air-actuated skirt to travel on an air cushion more than four feet thick. Obstacle clearance and ditch crossing capabilities for the SK-5 are excellent. In addition to the skirt-lifting system and the rudders mounted in the slipstream of the propellers, finger skirts and puff ports also aid in SK-5 control, being especially helpful in low-speed maneuverability. Flotation is assured by three buoyancy chambers, comprised of watertight compartments, extending almost the entire length and width of the SK-5.

     Here's a photo of an SR.N5 (the real, civilian version) with the side compartments/skirts removed:   http://s30.photobucket.com/user/india42/media/IMG_2938%20SRN-5_zpskrnmlct4.jpg.html

     A set of good pictures of the military versions in Vietnam:  http://1project2far.blogspot.com/2015/05/air-cushion-cavalry-us-armys-bell-sk5.html

     The front entrance is a two-part door:  a section with three of the windows hinges up (blocking the forward traverse of the top gun turret), and a lower part folds outwards to form a ramp. The transport version of this craft can board a jeep or mechanical mules (when most of the troop seats are removed), but the center of the cabin on the assault version is partially blocked by the lower components of the top turret (most notably, the foot stirrups).

     There are five hydraulic landing jacks, with big rubber pads, to support the vehicle when landed.

 

Assault Configuration

 

   This version is manned by five persons -- the pilot; the observer (who operates the Autonav, radios, radar, computer, etc.); the top turret gunner; and two waist gunners. It can carry 6 troops on seats in the cabin (plus more on the deck if they're willing!). Up to four stretchers can be fitted in the cabin, at the cost of troop capacity and the side guns; a davit hoist helps load stretchers or cargo aboard.

 

Transport Configuration

 

     This version has a crew of two -- pilot and observer (the waist guns are intended to be manned by the passengers). It can carry 15 troops in the cabin (plus more on the deck if they're willing!). Up to eight stretchers can be fitted in the cabin, at the cost of troop capacity and possibly the side guns; a davit hoist helps load stretchers or cargo aboard.

 

Dimensions

 

  • Length:  11.8 meters

  • Beam: 7.25 meters with inflated trunks

  • Height:  4.85 meters

  • Cabin:  3.65 meters long long by 2.4 meters wide

  • Front hatch:  1.75 meters high by 1.7 meters wide. Note that a CJ-3 jeep is 1.45 meters wide.

 

Weight

 

  • Basic, craft empty:  4640 kg

  • Gross weight (normal):   7730 kg

  • Additional load (overload):   1820 kg

  • Gross weight (max. overload):  9550 kg

  • Passenger capacity:  15 plus 4 crew (transport version)

  • Cargo capacity:

    • at normal gross weight:  1500 kg for transport version, 900 kg for assault version.

    • at overload max weight:  3320 kg for transport version, 2720 kg for assault version.

       

Power Plant

 

  • Generator:  two Morrow Project Fusion Generator Mk 1, each capable of producing 500 kW of power. Total mass 400 kg including cooling system.

  • Propulsion motor: one Westinghouse electric motor, 850 kW, weight about 500 kg including accessories

  • Propeller: one three-bladed Hamilton Standard variable pitch, 2.75 meter diameter

  • Lift motor:   100 kW

  • Lift fan: one 2.13 meter diameter centrifugal

 

Performance at Normal Gross Weight

 

  • Maximum speed: 111 kph -- with only one working fusion generator, 78 kph

    • aggressive maneuvers at speeds above 100 kph are unsafe

  • Cruise speed:  93 knots. Speeds above this require a very flat surface (such as a very calm day on a lake).

  • Max gradient hover conditions: 1 in 7.5

  • Wave clearance at 40 knots:  1.4 meters

  • At 93 kph, stopping distance is 150 meters. By dragging the skirt on water, stopping distance can be reduced to 50 meters.

 

Obstacle Clearance

 

  • Solid wall: 1.1 meters

  • Earth mound: 1.5 meters

  • Vegetation: 2 meters

  • Ditch: 4 meters wide x 20 cm deep at 37 kph

 

Armor

 

The sides (except for the windows), rear, roof and floor of the crew compartment have 3.26mm of aluminum 5083 armor (equivalent to 2.5mm RHA steel - armor value 10); the generator and motor compartment, lift fan housing, and the propeller shaft, are similarly protected. The windows are made from 8mm thick polycarbonate (armor value 10). The two front center windows (in the hatch) can fold up and inwards; the windows on the side, next to and across from the pilot, are in two parts and can slide open; the waist windows move on tracks upward (kind of like a garage door), to lie flat against the cabin overhead.

 

Armament

 

  • On the dorsal surface of the assault version is a Martin 250 electrically-operated power turret, with two .50 cal AN-M3 machine guns and 400 rounds per gun. The complete turret, including guns and 800 rounds of ammunition, but not the gunner, weighs 300 kg and is 1.2 meters in diameter at the mounting ring. There's a 9mm thick RHA steel "apron" protecting the gunner's chest and abdomen from his front (armor value 15); the acrylic dome provides some protection (armor value 7). Interrupter cams prevent the guns from firing into the propeller or other structures of the hovercraft. A reflector sight is mounted in front of the gunner's eyes.

  • The waist gun positions of the assault version each have a slide rail and gun cradle, rather like the waist gun positions on a B-17 bomber. Each position can mount a:

    • .50 cal AN-M3 machine gun, with 800 linked rounds per gun in a beltway and ammo box.

    • 40mm Mk 20 grenade launcher, with 400 linked rounds per gun in a beltway and ammo box.

    • a 7.62mm minigun was used by the U.S. military aboard some SK-5 versions, and considered by the Morrow Project -- but supporting a weapon used by no other Project vehicles was considered not worth the extra rate of fire.

 

 

SK-5 minigun mounting considered and rejected by the Morrow Project

 

  • The assault version comes with four tripods, four .50 caliber machine guns, and two 40mm grenade launchers; switching the guns, beltways, etc.at the waist positions takes about a half-hour. Vehicle equipment normally includes four sets of barrel bushings to allow "heavy" M2HB barrels to be used in all the hovercraft's .50 caliber guns.

  • The transport version has simple pintle mounts in the waist window positions; there are no feedways, and two MAG58 machine guns are carried to be fitted into the waist positions. 200 round steel ammunition cans are carried on the pintle mounts. Two M2 tripods are carried.

 

Systems

 

  • A six-position intercom system (pilot, observer, three gunners, and one at the rear of the cabin) connects the crew.

  • There is a heating, air conditioning, air filter and NBC system, mounted behind the rear cabin bulkhead. It has a washable filter, which should be cleaned after any suspicion of exposure to toxic agents, or to excessive dust. Note that the system doesn't know whether the vehicle is sealed or contaminated. It does have the equivalent of an M1 CBR Kit, which monitors external conditions; a display/control  unit similar to the MI CBR Kit is mounted at the observer's console. The CBR sensor can be connected to an M42 chemical alarm (a loud noise, blinking light kinda thing) by a simple "field telephone" two-wire cable, 5 meters long (but longer cables could easily be arranged). The NBC system provides a slight overpressure within the cabin, to keep dust and toxins out (somewhat). With the side windows or front hatch open, bio-safety is not likely, especially when in motion.

  • There are two 20 liter water tanks behind the rear bulkhead of the cabin. One (the "dirty" tank) fills from the outside; a washable ceramic filter connects from that tank to the 'clean' tank; the filter can treat 10 liters of water per hour. Keep in mind that the filter will not remove chemical contaminants, viruses, and other small things. Two GHT water taps are fitted in the rear area workspace, feeding from the 'clean' water tank; one provides 65° C hot water. There is a single spare filter; the filter in use should be swapped at regular intervals, or when the local water supply is known to be contaminated, and the dirty filter washed thoroughly with clean water.

  • Normally, a PRC-70 radio is installed, with amplifier, an LS-166/U speaker, 8 meter antenna mounted on the cabin roof, H-250/U handset, Morse code key, and other accessories. There is a converter box to connect this radio with the Morrow Project PC. Note that the PRC-70 cannot receive marine radio VHF transmissions. The pilot has a basic (not frequency setting) remote control station for the PRC-70.

  • The ARN-89 radio direction finder will also be installed, along with an Autonav A1B, a Furono FR-802D radar, a Laserdisc drive and several laserdiscs, the Morrow Project PC (a TRS-80 Model 4P), and an ordinary marine radio with scanner.

    • The marine radio runs on 12 volt DC power or 6 D-cell batteries. Includes built-in speaker, handset, earphone/headset plug, antenna, "cigarette lighter" power cord. Transmits "high power" (25 watts) or "low power" (1 watt).  Receives on 540 kHz to 1600 kHz (AM radio broadcast stations), receive and transmit (simplex) as SSB 1.6 MHz to 5 MHz (HF ship-to-shore) and FM 148 MHz to 174 MHz (the usual "marine VHF channels"). Range 2 km at low power, about 50 km at high power; the HF range varies quite a lot, especially at night. Weight about 5 kg.  

  • various items controlled from the pilot's console:

    • Normal maritime running lights (port, starboard and toplight) and twin halogen headlamps. There is also a double-flashing amber light on the top of the starboard steering fin -- useful as a signal for dismounted personnel without radios.

    • Three bilge pumps; each can drain 189 liters of water per minute. One serves the center buoyancy compartment and the cabin, the others serve the side compartments. Each pump has a Morrow Project "vehicle battery" as back-up power with a local switch, and can operate for a couple of hours without power from the fusion generator.

    • Wipers are fitted to the four forward windows, along with a wiper fluid reservoir.

    • There is a repeater display for the Autonav and radar.

    • An external loudspeaker, horn and siren.

 

Equipment Carried

 

     This is all stuff that is expected to stay with the vehicle most of the time, for all versions. Underlined equipment is in the forward storage compartment (ahead of the pilot); italicized items are in the deck panniers.

 

  • 6 or 15 life preserver vests, adult size, tan Resistweave

  • 1 life ring

  • 4 life rafts, rubber, CO2 inflatable

  • 1 signal mirror, Mk 3

  • 1 swimmer safety harness

  • 15 meters swimmer tending line

  • 2 ball whistle

  • 1 manual fog horn

  • 1 SK-5 operation and maintenance manual

  • 1 boat hook, 2.5 meters

  • 1 towing bridle

  • 1 polypro towing line, 70 meters

  • 1 anchor with 70 meter anchor line

  • 3 mooring lines

  • 1 kapok heaving line

  • 2 fire extinguishers

  • 1 chamois cloth

  • 1 operator checklist

  • 1 knee board

  • davit hoist (kind of like an engine hoist)

  • 1 tool box

  • 6 liters of lubrication oil, in metal can

  • gallon can of polyurethane laquer (propeller treatment)

  • brush for propeller treatment

  • 1 blanket

  • 1 hand bilge pump

  • 1 hatchet

  • 1 set of spare fuses

  • 1 wet suit for each crew member carried, 1/8" thick neoprene; dry suits and warm clothing are acceptable

  • 9 or 15 anti-exposure suits, bright yellow "gumby" type. These are "one size fits almost all".

 

Maintenance

 

     Inspection, maintenance, lubrication and repair are needed at about 0.1 man-hours per hour of operation. This includes a 30 minute walk-around before every flight day.

     Every couple of weeks, or if damage is inspected, the underside of the center hull should be inspected -- this takes a couple of hours on a flat surface.

     Every six weeks a more thorough maintenance inspection should be carried out -- hose down with fresh water, check for corrosion, inspect skirts, keel, fingers and hinges in detail; inspect and tighten up rudder and elevator controls; examine buoyancy tanks; drain various areas that collect water; calibrate and check the control systems; check safety equipment (including rafts); inspect fan and propeller for damage or distortion; apply polyurethane coating to propeller blades; test fire extinguishers; apply lubricants and grease; inspect and clean the radar antenna; inspect and test radios and other electronics

     Items most often in need of repair include the skirts, windows and wiper blades, lights, radios and radar, and general electrical system.

 

Training

 

     40 hours of indoctrination, systems familiarization, and maintenance training to act as 'crew'; 10 hours for 'observer' training (mostly radar); and 50 hours for pilot training. Thus a qualified SK-5 pilot has received 100 hours of training; this is all in addition to the usual Project training with weaponry, radios, etc.

 

Checklists

 

Preflight

 

  • grounding cable  remove/stow

  • windshield wipers and wiper fluid     examine/fill

  • anchor and line     secure

  • radio antennas     secure

  • navigation light     examine

  • electrical access hatch     secure

  • motor and transmission cowlings     secure/examine

  • drain and vent pipes     examine

  • intake filter on lift fan     examine/secure

  • lift fan structure    examine

  • nacelle support structure     examine

  • propeller lashings     remove

  • propeller hub     examine

  • beacon and light     examine

  • propeller blade leading edge     examine

  • accessories access hatch     secure

  • search light     examine

  • pitot tube cover     remove

  • windshields and turret canopy     examine

  • Martin 250 turret     examine/test sight

  • Martin 250 magazines     test boosters/fill

  • turret guns      examine/safe

  • waist guns ammunition boxes     fill

  • waist guns     examine/safe

  • peripheral skirts     examine

  • piano hinge attachments and pins     examine/secure

  • puffports     examine

  • pannier and stowage covers     secure

  • rudder     examine

  • rudder connecting rod     examine

  • rudder support struts     examine

  • elevators     examine

  • back skirts and keel skirts     examine

  • ramp hinge attachments and pins     examine/secure

  • fire extinguishers     secure

  • life jackets     stowed

  • immersion suits     stowed or worn

  • first aid kit     stowed

  • miscellaneous equipment     stowed

  • FOD check (esp. items on deck or cabin roof)     examine

  • tie down lines     remove/stow 

  • rudder bar     unlocked

 

Start Checks

 

  • rudder bar and seat     adjust

  • seat belt     fasten

  • controls     free

 

Start Procedures

 

  • throttle     closed

  • fire detection test     press to test

  • control circuits power     on

  • pilot MP ID cart     insert

  • start switch     on

  • intercom      test

  • beacon     on

  • nav lights     on

  • observer MP ID card     insert in Autonav

 

Drawbacks

 

     Known issues with the SK-5; these will be inspirational for the referee!

 

  • tears on the skirt are common; less than 2 meters long isn't too bad, more than 3 meters long will affect lift and handling

  • icing of the superstructure and windshield, ice and debris ingestion by fan and prop

    • it's typical to have 500 kg of ice on the exterior if traveling over freezing water

  • travel over not-actually-flat ice is bad at speed (the underside gets torn up)

  • preponderance of fatigue factors (noise, not a smooth ride, spray if the windows are open)

  • difficulty of controlling the craft (a well-trained pilot helps a lot)

  • inadequate fender system for protection of craft alongside structures

  • lack of open working space on deck, and difficulty in loading heavy loads while in hover

  • difficulty of obtaining parts

  • corrosion if operated in salt water

  • tendency to slide downhill on slopes

  • has good buoyancy in theory but 85% of reserve buoyancy is the main cabin -- the Coast Guard and MP filled the buoyancy tanks with resin-coated polyurethane foam blocks, which helps a lot.

  • requirement for frequent inspections of underside, especially after travel over debris or jagged ice ... the hull is mostly thin aluminum (except the cabin deck and sides)

  • wet suits, dry suits, or exposure suits must be carried for all ACV crew and passengers at all times; they will be worn when water is below 60 F, or the air is below 32 F

Comments (1)

Michael said

at 8:16 pm on Jun 14, 2016

Still gotta do a lot of converting from the real, turbine powered beast to the Project version.

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