Section III. TECHNICAL PRINCIPLES OF OPERATION

TM 55-1730-228-13&P

Section III. TECHNICAL PRINCIPLES OF OPERATION

1-12. FUNCTIONAL DESCRIPTION.

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a. General. The SPEMS (Figure 1-2) is a gasoline engine powered, 4-wheeled, hydraulic maintenance stand

equipped with an adjustable platform and stabilizers. The SPEMS is designed to help maintenance personnel in the

performance of overhead maintenance tasks, especially CH-47 and CH-54 helicopter rotor maintenance, in the easiest,

safest, and most efficient manner possible. The SPEMS consists of four major assemblies; platform assembly, scissors

assembly, frame assembly, and engine rack assembly.

b. Platform. The platform is divided into two parts, the basic deck and the deck extensions.

(1) Basic Deck. The large, flat, rectangular platform is equipped with removable, split guardrails around the

platform. The guardrails can be completely removed, if needed, for compact storage and shipment. In addition, the top

half of the railing can be removed for rotor blade or other obstacle clearance when approaching or withdrawing from the

work. Female receptacles with self-closing covers are flush-mounted on the floor and provide power to the work lights.

Two work lights and four work light brackets are provided. The work lights are secured to the brackets with thumb

screws. A grounding reel mounted to the guardrail is connected between an approved grounding source and the aircraft

to prevent static electrical discharges. The platform control box is equipped with a bracket that allows the control box to

be positioned anywhere on the guardrailing. A removable deck plate allows for the SPEMS to interface with Chinook

CH47 helicopters. Contact bumpers at the front and rear of the platform, and all three sides of the cutout (with the deck

plate removed), override the SPEMS controls when activated with two pounds of pressure. If the front bumper touches

an obstacle while moving forward, all SPEMS operating modes, except reverse movement and deck traverse backward

(if moved forward), are rendered inoperative.

(2) Deck Extensions. Two manually operated deck extensions are located at the left and right sides at the front

of the platform. A spring-loaded pin secures the extension in the retracted or extended position. Each extension is

equipped with a contact bumper that overrides SPEMS controls when activated.

c. Scissors. Platform lifting is accomplished with the scissors assembly. Twin hydraulic cylinders supply the force

needed to extend the scissors thereby lifting the platform. Each cylinder is supplied with a hold valve to prevent free

descent of the platform at all times, even in -the event of a downstream hose rupture or other component failure. In

emergency operation (loss of power), when the platform is elevated, the emergency hand pump releases the hold valve

and allows the platform to be lowered.

d. Frame Assembly. The frame assembly is designed to support the platform with personnel and equipment. The

frame assembly, wheels and tires are designed for traveling in any terrain; however, must be on firm level ground when

raising or lowering-the platform. Stabilizers provide supplemental support only and are not intended to level the base.

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