Aircraft technical Basics: Introduction to Airplanes - Navy Training Courses Edition of 1944: Chapter 12 Cleaning and Inspecting

CHAPTER 12 CLEANING AND INSPECTING

WHY KEEP 'EM CLEAN?

A FLIGHT INSPECTION must be made EACH DAY before any flying is done in a service airplane. But before an inspection can be carried out properly the airplane must be thoroughly clean, INSIDE AND OUT. In case you're wondering why cleanliness is so important in airplanes, there are a number of answers. Any one of them is sufficient in itself to justify rigid cleaning rules.

It is easy to overlook something like a cracked landing gear fitting if it's covered with MUD or GREASE.

Vibration may cause cracks in the skin, loosen nuts, cause hinge fittings to wear and develop elongated bolt holes. DIRT HIDES THESE DANGER SIGNS if the airplane isn't cleaned properly and often.

The flying speed of an airplane - yes sir, the thing it needs most in combat - may be SERIOUSLY affected if a dirt film is allowed to collect on it's outer surface.

Dirt, trash, or loose gear- blowing or bouncing around inside the airplane is both annoying and DANGEROUS. A little dirt in the eyes of a pilot or crewmember at a critical time can cause all kinds of trouble.

Dirt collecting and allowed to remain on lubricated controls encourages CORROSION and WEAR.

The combination of dirt and grease on movable parts often results in making a "grinding compound" that causes a FAILURE if not caught in time.

WASHING DOWN

First, you can get going by WASHING DOWN a plane, as the boys are doing in figure 40. Usual practice is to WET THE OUTSIDE THOROUGHLY with a water hose. Don't turn on the water, though, until you've made certain that all doors, hatches and windows are closed. When you're using the hose, try to AVOID WETTING THE ENGINE. Engines are built to withstand heavy storms, but there is no point in soaking the electrical connections unnecessarily.

Use a ladder or scaffold to stand on, and begin washing on the TOP SURFACE of the wing. If oil and grease have been thrown back on the cowling and tail surfaces by the engine, soap and brush may not be enough to remove them. It may be necessary to use an approved CLEANING SOLUTION. Scrubbing with soap and brush will normally do the trick, however.

Be careful not to let any water enter the WING by getting in around strut or fitting openings. Water inside the wing will cause deterioration. When all surfaces have been scrubbed with soap ,(or cleaning solution) and thoroughly rinsed with clear water, the airplane should be WIPED DRY with a clean chamois or rags wrung out in clear water. Don't step on the cowling or wing skin while you're washing and wiping them. They're easily dented, and hard to repair. Airplane fabric should be wiped off daily and washed at least once a week. NEVER USE GASOLINE for cleaning doped or painted surfaces, or salt water for washing and rinsing.

Figure 40.-Washing down a flying boat.

PREVENTING CORROSION

When an airplane is operating around salt water, metal parts tend to CORRODE rapidly. Such metal should be inspected frequently for signs of corrosion, particularly if not painted. Dirt and rust should be removed immediately, and the surfaces coated with OIL or a RUST PREVENTIVE.

On aluminum alloy surfaces, signs of corrosion will first appear in the form of a white powdery substance (aluminum hydroxide). You should watch for these signs carefully, particularly on rivets, seams, fitting, and propellers. If corrosion has started, take IMMEDIATE steps to check it. Wash the area, see that ALL. traces of corrosion are removed, take care that you do not damage the metal while cleaning it, and have the area treated to prevent further corrosion. If priming and painting are required, you can refer to "Process Specifications" for full and latest details on WHAT and HOW.

CLEANING ENGINES AND PROPS

Now to clean up the ENGINE. It should be washed down with a spray, using fresh water or approved cleaning solution. Magnetos, starters, and generators should be covered. Clean around them with a bristle brush to keep the spray pressure from driving the cleaning solution inside the housings. Wash the TOP cylinder first, and avoid spraying electrical equipment. Then you can dry the engine, using CLEAN rags - NOT waste. How often should the engine be cleaned? That will depend on conditions under which the airplane operates. In other words - whenever necessary, remembering that the engine and it's accessories MUST be kept clean at all times.

Next comes the PROP. The life of a propeller depends largely on the care given it IMMEDIATELY after EACH flight. An aluminum alloy propeller, when used in salt air, will become coated with a light film of powdery aluminum hydroxide. In itself, this fine white powder does little harm and you can remove it easily by wiping the blade with a coarse cloth, followed by rubbing with oil. Old oil drained from aircraft engines is one of the best kinds for this. The free carbon in such oil acts as a mild abrasive, the traces of sulfuric acid present, remove the hydroxide deposit, and the oil film left on the propeller blade keeps the salt air from it.

WATER SPRAY, striking a whirling propeller blade, does so with such force that small pits are often formed on the blade's leading edge. If you don't do anything about them these pits RAPIDLY grow bigger through corrosion. Blades subjected to salt water spray should be rubbed down with crocus cloth and oil after every flight. Otherwise the pits will get so big you'll have to remove them with a file. In turn, filing may necessitate rebalancing the blade - which is a considerably bigger job than you might guess.

Steel propeller blades have somewhat more resistance to abrasion and corrosion than aluminum alloy blades and, if rubbed down with oil after each flight, will retain a smooth surface for a longer time. On either steel or aluminum alloy blades, oil tends to oxidize in any cracks present, making them stand out as dark lines and thereby easing the job of inspection for defects.

Propeller HUBS should also be inspected regularly for cracks and other defects. You won't be able to find defects unless the hub surface is kept in its original bright condition. That's why paint is never used on hubs. If the plating is damaged or removed, be sure to keep the surface oiled.

CLEANING ENCLOSURES

Next job? Cleaning the COCKPIT ENCLOSURES, TURRETS, WINDOWS and other PLASTIC applications. And this is a chore to be handled carefully if ever there was one. Be gentle ! Remember, the pilot, gunners, and other crew members depend upon being able to SEE through these "windows." Rough handling won't do!

The sheet plastic materials of which these parts are made react to too much buffing or polishing by LOSING their transparency. You can't restore the original luster or successfully remove minor scratches by applying elbow grease, CAREFUL cleaning - in accordance with standard methods - will reduce to a minimum the necessity for polishing, so believe the book and follow the rules. Otherwise you'll have the pilot flying blind at high noon on a sunny day.

Before you start actual cleaning operations, FLUSH the plastic enclosures thoroughly with fresh water. On Naval airplanes, salt from sea water crystallizes and deposits on enclosure surfaces. Flushing with fresh water dissolves the salt and helps prevent scratches. Then go over the plastic with a water solution of MILD soap, using a CLEAN grit-free cloth, chamois, absorbent cotton or - best of all - your BARE HANDS. Rinse with fresh water, and dry with a damp chamois or some absorbent cotton - NOT with a dry cloth. A dry cloth may cause scratches, and it will build up an electrostatic charge that attracts dust particles to the surface. 

Oily or greasy dirt may be removed from plastics with kerosene, naptha, hexane or - if you don't have these materials at hand - with UNLEADED GASOLINE. WARNING ! DON'T USE aromatic fuel for this purpose. Absorbent cotton is best for applying solvents, you'll find. If there's a lot of dirt and grease on a plastic enclosure, you may have to follow up with a regular soap-and-water wash job to make the surface spic-and-span.

When you're nosing around, looking for a grease solvent that you can use on the plastic enclosures, don't grab the first thing you see. The substances mentioned above as being suitable have some dangerous cousins. NEVER, for instance, use acetone, benzene, lacquer thinner, toluene, ethyl acetate, ordinary kitchen cleaner or commercial window sprays. They will RUIN the plastic material or at least will MAR the surface.

As soon as you've cleaned the plastic surfaces, apply a coat of WAX to them. It will cover minor scratches, give the surface a good gloss, and HELP PREVENT further scratches. The following waxes have proved satisfactory for the purpose

"3-M Automobile Wax."

"Simoniz Wax" - (not "Kleener"). "Wilco Plastic Polish."

"Johnson's Paste Wax."

Any static electric charge caused by the waxing can be removed with a damp, clean chamois.

INSPECTING

Each day, before any flight is made in a Naval airplane, a DAILY FLIGHT INSPECTION FORM (N. Aer. 3119, or "Yellow Sheet") must be filled out and SIGNED. The data on this form apply to all service-type airplanes, but many operating units use an additional sheet for recording details peculiar to the particular airplane they're using.

The plane captain, or whoever is officially detailed to make inspection, fills out these forms. He checks the form to be sure everything is ship-shape before signing on the dotted line.

There are still more spaces to be filled in on the form before the day's over. A HISTORY OF THE FLIGHT is entered - including times of takeoff and landing, total time, purpose of flight, average rpm of the engine, fuel and oil pressures, and oil temperature. Also noted are the names of the first and second PILOTS, and of any PASSENGERS. A permanent record of this information is also made in the plane and engine logs.

After the flight, the pilot signifies, in writing, on this form that the airplane is either SATISFACTORY in all respects or that DEFECTS have been observed. If the latter, a remark concerning each defect is entered.

No doubt, you will be detailed to carry out an actual inspection. Here's a basic check list - and don't miss a point. A miss may mean a WRECKED AIRPLANE, and maybe LOSS OF LIFE.

 - PROPELLER

Inspect BLADES for pits, cracks, nicks, and proper oil film.

Inspect prop HUBS and ATTACHING PARTS for defects, tightness, and proper safetying.

Check VARIABLE PITCH PROPELLERS for adequate lubrication.

Check propeller SPINNER for security of attachment.

 - ENGINE -

Inspect ENGINE COWLING - including ring cowl and flaps - for cracks and security.

Inspect EXHAUST STACKS for cracks and security. Check SPARK PLUG TERMINAL ASSEMBLIES for cleanliness and tightness.

Inspect accessible IGNITION WIRING AND HARNESS for security of mounting.

Clean MAIN FUEL LINE STRAINERS.

Drain a small quantity of fuel from BOTTOM DRAIN and inspect for presence of water and foreign matter.

Check FUEL AND OIL SYSTEMS for leaks, tightness of tank caps, and to make certain that VENTS are clean of obstruction.

Check security of OIL DRAIN PLUGS.

Check FUEL and OIL supply (do not rely on gages). Turn handle of disk-type OIL STRAINER (if installed) at. least one revolution to clean it.

 - LANDING GEAR -

Inspect TIRES for defects and proper inflation.

Check WHEELS for cracks and distortion. See that hub caps are secure.

Inspect SHOCK ABSORBER UNITS and BRAKE LINKAGE GEAR. Check STRUT RETAINING BOLTS and fittings for security. Inspect BRACE WIRES for tension and security.

Check the RETRACTABLE LANDING GEAR mechanism and lubricate as necessary.

Inspect MAIN FLOAT (or floats) or HULL. for leaks, presence of water, and security of handhole covers and vents.

Check BEACHING GEAR tires, wheels, locking-pins, and attachment fittings.

 - WINGS -

Inspect COVERING for damage, buckled ribs and end bows. Look over the ATTACHMENT FITTINGS for security. Check AILERON HINGES, PINS, HORNS and TABS for security of attachments, proper lubrication, and position. Inspect and check operation of LANDING FLAPS rr DIVING FLAPS. See that there are no hydraulic leaks.

See that all accessible CONTROL CABLES, TUBES and PULLEYS are secure and properly lubricated.

Check WING-TIP FLOATS for leaks, presence of water, and security of handhole covers and vents.

Remove all SURFACE CONTROL LOCKS before flight.

- TAIL -

Inspect COVERING for damage, buckled ribs, and bruised edges.

See that ATTACHMENT FITTINGS are secure.

Check STRUTS and BRACE WIRES for security of terminal connections.

Check the control SURFACE HINGES, PINS, HORNS and TABS for security of attachments, proper lubrication and position.

Inspect CONTROL CABLE, TUBES, and PULLEYS for security and proper lubrication.

Check TAIL SKID or WHEEL assembly for condition and lubrication, noting position of locking device. Remove all SURFACE CONTROL LOCKS before flight.

- FUSELAGE -

Inspect all BAYS for loose articles.

Check the OXYGEN EQUIPMENT and service.

Inspect the CONTROL COLUMN assembly and accessible parts of control system for freedom of movement, lost motion, security of attachments, and proper lubrication.

See that RUDDER PEDAL assembly and CONTROL SYSTEM operate properly. Check for freedom of movement, lost motion, security of attachments, and proper lubrication.

Prior to carrier operation, check working condition of LANDING HOOK, and inspect its mechanism.

Test operation of NOSE SHUTTERS.

Inspect FLOTATION GEAR and FIRE EXTINGUISHER BOTTLE INDICATORS for fully charged condition.

See that all removable COWLING, FAIRING, and INSPECTION PLATES are secure.

Check proper functioning of LIGHTING SYSTEM.

Make certain all SAFETY BELTS are secure.

See that COCKPIT ENCLOSURES and the ADJUSTABLE SEAT mechanism function properly.

Check position of GENERATOR BATTERY-CHARGING SWITCH.

Make sure there is the proper quantity of fluid in the HYDRAULIC SYSTEM RESERVOIR.

- WARMING UP -

See that CHOCKS ARE UNDER WHEELS.

Check to be sure IGNITION SWITCHES are in the "off" position.

Pull PROP through by hand for at least three complete revolutions.

Warm up and check proper functioning of ENGINE, or engines.

Test engines on EACH FUEL TANK, and place on designated tank for take-off.

Check ENGINE CONTROLS for proper functioning and to detect any lost motion.

See that VARIABLE PITCH PROPELLER operates properly. During warm up, open the engine's cowl. SKIRT FLAPS. Check position of CARBURETOR AIR CONTROL.

Make certain that CARBURETOR MIXTURE CONTROL functions properly.

Check operation of VACUUM PUMP (if installed) at a speed sufficient to operate instruments.

IDENTIFYING PIPE LINES

Although there are regular mazes of PIPE LINES running through the insides of modern airplanes and their engines, you won't have any difficulty in telling them apart if you get thoroughly familiar with the SYSTEM used for IDENTIFYING them. It's not done with mirrors and wires, and there's nothing baffling about it. Each pipe has it own particular kind of "dog tag" in the form of COLORED BANDS painted around it. Various COMBINATIONS OF COLOR have been universally agreed upon to DIFFERENTIATE ONE PIPING SYSTEM FROM ANOTHER.

The color bands are one-half inch wide. They are PAINTED NEAR EACH END OF A PIPE, and also at INTERMEDIATE POINTS where they'll be helpful in following the pipe through the system. A little study of figure 41 will familiarize you with the whole setup.

PERIODIC INSPECTIONS

In addition to daily flight inspections, REGULAR CHECKUPS on Naval airplanes are required at DEFINITE INTERVALS. YOU will obtain "PERIODIC AIRCRAFT INSPECTION FORMS" from the Bureau of Aeronautics, but you'll find there are features on certain airplanes that are NOT covered by the forms and sometimes it's necessary to ADD to the list of points to be inspected. In some other instances you'll want to MODIFY the forms to meet the requirements of a particular case.

Figure 41.-Markings of aircraft piping systems.

It will be necessary to have further inspection forms prepared and printed for checks and inspections, which are required at intervals NOT COVERED BY THE BUREAU FORMS - such as for the 60-hour and 120-hour inspection. If you are having these forms prepared, be sure to include the items covered by the Bureau forms as well as the items requiring inspection at these special intervals.

Under some circumstances, such as when the climate or service conditions are adverse or unusual, certain parts of airplane equipment may require inspection MORE FREQUENTLY THAN SPECIFIED by the Bureau of Aeronautics. If you're working under such conditions, additional forms should be prepared and ready for use.

Every airplane must be supplied with TAKE-OFF and LANDING CHECK-OFF lists for the pilot's use. These lists should be posted in the cockpit and maintained in an easily readable condition. They include all the point's to be checked - and the acts to be performed - by the pilot in landing and taking off.

ROUTINE CHECKS

The pilot will note any defects he discovers during flight. The plane captain also makes an inspection, and any defects he or the pilot have discovered MUST BE CORRECTED before the next scheduled flight of the plane. If there isn't enough time to make the airplane shipshape, the plane captain's duty is to make a FULL REPORT to the flight officer who is responsible for carrying out operations scheduled by the squadron commander. Even though nobody finds or reports any defects, there are still a number of routine inspections to be made from time to time.

After each flight you should check over all parts which have been treated with protective coatings of GREASE or WAX. If any corrosion is found, or the protective coating has deteriorated, take care of it - pronto.

Fuel tanks which don't have sumps and sump drains should be DRAINED AND CLEANED once every 30 days.

All PARACHUTES must be unpacked and inspected at least ONCE a month. That's orders ! New SELF - INFLATABLE LIFE JACKETS should be tested thoroughly at the end of their FIRST month in service, and at SIX-MONTH intervals thereafter.

Wheel-brake mechanisms need careful inspection throughout - every six weeks or less. In fact, to prevent possible deterioration, ALL accessible parts of the airplane should be inspected periodically. The squadron commander decides how often, but these checkups should all be conducted at least ONCE every six weeks - oftener if possible.

All fixed or portable FIRE EXTINGUISHERS (carbon dioxide type) must be tested every six months.

SAFETY BELTS - and remember, the accent is on SAFETY - must get careful visual inspection every TWO months or less for signs of deterioration and other possible flaws. TWICE a year they are put through a "static load" test to check for any indications of weakness in the webbing or the release.

PILOT'S SAFETY BELTS must stand up under a 500-pound test load. GUNNER-TYPE BELTS have to be able to pass a 400-pound pull. And SIDE STRAPS of gunners' belts must not fail under a load of 250 pounds. Be sure the RELEASE BUCKLE is still in free-and-easy working order after the tests are finished. There's no percentage in wrecking good gear while your checking it.

SELF-INFLATABLE LIFE JACKETS have gas-filled cylinders (carbon dioxide) which blow them up.

It's necessary to inspect the jackets FOUR or FIVE times a year to make certain there's no corrosion of the cylinder walls which might let the gas escape. Coat the cylinder and its container with light oil to protect them from such corrosion. IT MIGHT BE YOU that'll be wearing that life jacket in a pinch, so be guided accordingly.

On all INFLATABLE LIFE RAFTS the cylinder valve seals have to be inspected QUARTERLY. Replace the cylinder IF the seal is found to be broken. Rafts of this kind are given complete inspections and tests BEFORE being placed in service and SEMIANNUALLY thereafter. When in storage, ONCE-A-YEAR inspection is adequate. Here's the method you'll use for testing rafts

WEIGH THE CYLINDER COMPLETE. Put in a new one if it weighs one-half ounce less than the total weight stenciled on the side.

INFLATE THE RAFT to see if the inflation system is working correctly.

Remove the CYLINDER AND PLUGS from the manifold. TEST ALL MANIFOLD CONNECTIONS for airtightness by applying soapy water to them.

Inspect all EXPOSED METAL PARTS for evidence of corrosion, and examine the body of the raft for deterioration.

See that all the LOOSE EQUIPMENT IS PRESENT, COMPLETE, and in GOOD condition. Try the HAND PUMP to see that it's in working order.

Let the raft STAND INFLATED for 24 hours. There shouldn't be any undue deflation in that time.

Deflate the raft and REATTACH THE CHARGED CYLINDER. Treat the threaded plugs of the manifold with anti-sieze compound, and screw all connections tight.

POWDER THE RAFT thoroughly WITH TALC, and fold carefully so as to avoid chafing. Be certain that the inflating valve is IMMEDIATELY accessible.

Put a TAG on the raft with date of inspection on it. Then REPLACE the raft in its carrying case.