Propeller Maintenance: Tiger Moth Aircraft and Spitfire Mk XI - Coursework Example

Running head: Propeller maintenance College Introduction Aircraft propellers which are also known as airscrews transfer rotary motion from the turboprops or piston engines to provide propulsive force and they may possibly be variable pitch or fixed. Decades ago, the aircraft propellers were carved by hand from laminated or solid wood but presently propellers are being constructed from metal, aluminium or the most modern propeller designs which are made by using high-technology composite materials such as fiber. The propeller is more often than not attached to the crankshaft of a piston engine, either directly or through a reduction unit. Bowers (1979, p. 101) avers that the light aircraft engines frequently do not need the complexity of gearing but on larger turboprop and engines aircraft it is necessary. This paper strives to show how a technician can remove and put into storage the propeller from the Tiger moth aircraft, by using another one from a Spitfire Mk XI by ensuring the correct storage procedures are carried out, the storage conditions are suitable and all the relevant paperwork is complete. To understand more about the types of propellers and especially the ones that will be replaced, it is important to gain knowledge about these two different aircrafts. Tiger Moth Bransom (1991, p. 287) reveals that the de Havilland DH 82 Tiger Moth is a 1930s biplane designed by Geoffrey de Havilland and was run by the Royal Air Force (RAF) and others as a principal trainer for pilots The Tiger Moth stayed put in service with the RAF before replacement by the de Havilland Chipmunk in 1952, when many of the excess aircraft entered the civil operation. Numerous other countries used the Tiger Moth in both civil and military purposes, and it remains in extensive use as a leisure aircraft in many states. It is still rarely used as a primary training aircraft, chiefly for those pilots wanting to get experience before moving on to other tail wheel aircraft, even though the majority Tiger Moths have a skid and a lot of them are now in use by various companies offering trial lesson experiences while those in private hands usually fly far fewer hours and have a propensity to be kept in concours condition. The de Havilland Moth club founded 1975 is now an extremely organized owners association giving technical assistance and focal point for Moth enthusiasts. Tiger Moth aircraft Eltscher (1998, p. 167) discloses that there is one distinguishing feature of the Tiger Moth two-blade design in its differential aileron control setup and that the ailerons which are on the lower wing of a Tiger Moth are operated by an externally mounted circular bell crank, which lies flush with the lower wings fabric under-surface covering. This circular bell crank is rotated by metal cables and chains from the cockpits control columns, and has the externally mounted aileron pushrod attached at a point 45º outboard and forward of the bell crank’s centre whilst the ailerons are both at their neutral position which results in an aileron control system operating, with barely any travel down at all on the wing on the outside of the turn, and the aileron on the inside travels upwards to counter-act adverse yaw. Eltscher (1998, p. 156) adds that there is an interesting issue about the Tiger Moth’s propeller in that the aircraft has no electrical system and the engine has to be started by hand by turning the propeller which requires extra care so as to prevent being struck by it which may result in serious injury. Since the plane is a tail-dragging biplane, taxiing also requires superfluous care since the pilot cannot see directly ahead, and there is the possibility of the lower wing can hitting obstacles, and it is also vulnerable to gusts of wind on its inclined, large, upper wing. Spitfire Mk XI airplane Spitfire Mk XI The Super-marine Spitfire is a British single-seat fighter aircraft which was utilized by the Royal Air Force and many other Allied nations during the Second World. The Spitfire units did, nonetheless, have a lower propeller wear and tear rate and a higher victory to loss ratio than those flying Tiger Moths. Much loved by its pilots, the Spitfire served in various roles, including photo-reconnaissance, interceptor, carrier-based fighter, fighter-bomber, and trainer and it was built in various modifications, by using several wing configurations. Price (2002, p. 298) reveals that even though the original airframe was designed to be powered by a Rolls-Royce Merlin engine producing 1,030 hp (768 kW), it was adjustable enough to use progressively more powerful Merlin and the later Rolls-Royce Griffon engines; the latter was in due course able to generate 2,035 hp (1,520  kW). Spitfire Mk IX G-CTIX (PT462) Pre-installation check When one is about to deal with installing and removing a propeller, it is important to do some check so as to know the state of the prop. But before we do that, let us first know what propellers are. When it comes to designing propellers, since the maximum performance of the airplane for all situations of operation from takeoff; climb, cruising, and high speed are considered. Lovenitti (2002, p. 177) writes that the propellers can be classified under eight common kinds as follows: Fixed pitch propellers; The fixed pitch where the propeller is made in one piece and single pitch setting is feasible and is generally two blades propeller and is which is mostly made of wood or metal. A tiger Moth uses these kinds of propellers. Wooden Propellers: These were used almost wholly on business and personal aircraft prior to World War II. The wood propeller is not cut from a solid block but is built up of a number of separate and different layers of carefully chosen sorts of wood which are used in making the propellers The most suitable and preferred are yellow birch, black cherry, mahogany, and black walnut. The use of lamination of wood however reduces the tendency for a propeller to go out of shape but to get ordinary one-piece wood propellers, from five to nine separate wood laminations a 3/4 inch thick wood are made use of. Metal Propellers: These are solid steel propellers which used to be made in the 1940s particularly for military use. The modern propellers are made-up from high-strength, heat-treated, aluminum alloy by forging a single bar of aluminum alloy to the required shape. But the metal propellers are now widely used in the manufacture of propellers for all kinds of aircraft but the universal appearance of the metal propeller is like that of the wood propeller, except for fact that the sections are usually thinner. Five-blade pitch propeller The propeller pitch setting may be adjusted with tools while on the ground before the engine starts running and this sort of propellers more often than not has a split hub and the blade angle is indicated by the aircraft specifications. A technician can set the blade angles by loosening the clamps and the blade is then rotated to the desired angle and then the clamps are tightened. Six-blade pitch propeller  A constant speed propeller has the ability to assume a negative blade angle and thus create a reversing thrust and when propellers are reversed; their blades are rotated below their positive angle, through flat pitch, until a negative blade angle is obtained so as to generate thrust acting in the opposite direction to the forward thrust. Reverse propeller thrust is used when a large aircraft is landing, and there is the need to decrease the length of landing run. There is a also the Beta Control propeller which permits the manual repositioning of the propeller blade angle beyond the normal low pitch stop and is used mainly frequently in taxiing, where the thrust is manually controlled by adjusting blade angle with the power lever. As you will have noticed from the subject about propellers, it is apparent that they do a lot of work in the aircrafts and this result in wear and tear. Since now we know what propellers are, we can now do a pre-installation check. First, I will need to see if the propeller is in good condition. Is it bent, or are the holes that hold the six bolts worn out. I will also need to check and see if the Tiger moth propeller is ideal fro the Spitfire and vice versa. It is also important to know if the Spitfire propeller will fit te Tiger moth’s hub. In my case, the answer is a yes. It so happens that when a particular propeller is attached to an aircraft that is grounded like those in the museums’ or exhibitions, a lot of care needs to taken when either storing or restoring them to their original status. In this case when a technician who is working at a major historic aircraft museum, has been tasked to de-commission a Tiger Moth aircraft, which has been placed in storage for one year, and replace it with a Spitfire Mk XI for a new exhibition, careful steps must be taken to do so. According to Mario (2001, p. 189), the technician must first remove and put into storage the propeller from the Tiger moth aircraft, and ensure that the correct storage procedures are carried out, the storage conditions are appropriate and all the relevant paperwork is complete. Metallic Tiger Moth one piece fixed-pitch propeller Installing Tiger moth propeller To remove the propeller from the Tiger Moth aircraft, I will need to get onto a raised platform so as to reach the hub that holds the propeller in place. With my note book on hand, I will first time myself with a digital time-watch and facing the hub, I will try and find out the condition of the wooden two-blade propeller which is held in place by six bolts that are attached into the hub by clamps. The condition of the 1958 wooden propeller is not very good since it has been exposed to moisture and other weather elements. By using a tape-measure, I find that the propeller is 1.94 meter, with 8 bolts on a 120 mm circle and the central hole is 70mm while the hub is conical with 162 and 198 mm external diameters and the thickness is about 100 mm. There are six laminations in the wooden propeller; three about 22 and three about 12mm. The painting is loose everywhere, and the only way it seems of unscrewing the six bolts is with utmost care is I am not remove it safely. By doing this, I notice that one blade has fabric while the other and it must have been removed at the time of repainting, as there are some visible under the brass leading edges. Tiger moth fixed one-piece wooden pitch propeller using six bolts After installation checks After I have removed and replaced the Tiger Moth propeller with the Spitfire Mx, I must first investigate and evaluate the different methods and the maintenance procedures so as to determine the serviceability of propellers. First I will need to find out if the aircraft’s fabric covering is in good condition and that the propeller is covered well or not. Aircraft fabric covering is a term used for both the material used and the process of covering aircraft open structures and it is also used for reinforcing closed plywood structures, the de Havilland Mosquito being an illustration of this technique. Lovenitti (2002, p. 157) argues that the early aircraft used organic materials such as cellulose dope and cotton modern fabric covered designs more often than not use synthetic materials such as butyrate dope for adhesive and Nylon, and this technique is regularly used in the refurbishment of older kinds that were originally covered by using traditional methods Mario (2001, p. 327) says. After doing a thorough check, I find that the propeller I removed from the Spitfire and installed onto the Tiger moth airplane is in good condition. The six bolts are tight enough and the hub is in place. Even though the Tiger moth propeller had been made of wood, the one I have installed from the Spitfire is made of metal, but it fits well as a glove. Paper work Now that I have done the pre-installation and after installation checks, I will need to do my paperwork. The following is what I will write in my work book as paper work. ‘I have already determined the serviceability of the Tiger Moth one-piece wooden pitch propeller, I will then go to the store to find out the condition of the Spitfire six-piece metal pitch propeller so as to determine if it can be used to replace the one on the Tiger Moth. Metallic Silver 3.17mm propeller adapter I will then remove the clamps from the hub on the propeller and by using a ratchet spanner; I will remove the six bolts, one by one as I place one side of the propeller on my shoulder so as not to let it fall to the ground. After I have safely removed the one-piece wooden pitch propeller from the Tiger Moth and I have safely taken it to the store, I will then start to attach the six pieces of the metal propeller pitch of the Spitfire which has been in the store for one year to the Tiger Moth propeller hub, one by one until all the six pieces are attached properly. The removing of the Tiger Moth one-piece wooden propeller pitch and the replacing of the Spitfire six-piece propeller pitch takes me some 24 hours to accomplish successfully. And now, it is time to make sure that the two propellers are kept in good condition.’ The paper work is done for the moment. Storing the propeller It is important to note that the Tiger Moth aircraft has not been in service for many years and so I will need to ensure that the replaced Spitfire six-piece metal pitch propeller has been in store for over a year and it has to look just great for the coming exhibition. At the same time, I have to ensure that the one-piece fixed-pitch wooden propeller is restored to its good condition before putting it into the store where the Spitfire propeller had been. Karls (1996, p. 267) concludes that with the advancement of contemporary synthetic materials, the cotton fabrics have replaced in civil aircraft applications by Polyethylene terephthalate, which is also branded by the trade-name Dacron or Ceconite. This new fabric can be glued to the airframe instead of being sewn and then heat-shrunk to fit but the cotton can generally last six to seven years when the aircraft is stored outside, but I intend to use Ceconite, which does not rot like cotton, and can last over 20 years. Mario (2001, p. 356) reveals that these eearlier attempts to use these modern fabrics with butyrate dope proved that the dope did not adhere at all and peeled off in sheets. Checks before removing the tiger propeller As far as the Tiger Moth propeller is concerned, I intended to use one fabric system, developed by Ray Stits in the United States of America and marketed under the brand name Poly-Fiber. This utilizes three weights of Dacron fabric sold as by the brand name Ceconite, plus fabric glue for attaching to the airframe (Poly-Tak), fabric preparation sealer resin (Poly-Brush) and paint (Poly-Tone). This method John (1983, p. 190) avers is not dope and instead uses vinyl-based chemicals. Ceconite 101 is a certified 3.5 oz/yd² (119 g/m²) fabric while Ceconite 102 is a 3.16 oz/yd² (107 g/m²) fabric. There is also an uncertified light Ceconite of 1.87 oz/yd² (63 g/m²) projected for ultra-light aircraft. This method requires physical attachment of the fabric to the airframe or propeller in the form of rib-stitching, rivets or cap strips, which are then usually covered with fabric tapes. The Tiger propeller has now good a very high gloss on the wooden one-piece Tiger Moth pitch propeller and I can now store it where the Spitfire propeller had been concludes’ (John 1983, p. 198). Paper work John (1983, p. 230) This is the final part of my paper work and I will write as follows; ‘the modern covering techniques after the installation of the propeller follows the traditional method with minor differences and while synthetic materials are used, the covering is adhered to the structure by using dedicated glues. The shrinking procedure is accomplished by applying a heat gun or electric iron, and once the covering is tight the rib-stitching is once more used for faster or heavier aircraft and cosmetic finish coats are generally applied. However, a side effect of using modern covering materials on wooden structured propellers is that due to the much longer life the structure remains covered and un-inspected for much longer time periods, and this has resulted in unusual periodic inspections being mandated by aviation regulatory bodies. With both techniques of covering, it is normal for the aircraft to be re-weighed after renewal of the fabric to establish for any change in mass and centre of gravity, This is important to do so as to be sure whether the propeller you are about to install is in proper condition Mario’ (2001, p. 199) avers. Now is the time to put my paper work down and go to my summary. Summary Since I have already removed the Tiger Moth one-piece wooden propeller pitch, I will need to make sure that it is stored in good condition for future use since it has not been serviced for many years since the wooden prop has some hair line cracks forming at the tips. From my research, I have learned that since the damage is not severe in nature, they can be repaired easily with some house hold ingredients, such as Crazy Glue and baking soda. There are two kinds of repair that may be done by using these two procedures. One is the repair of a propeller split at the tip of the wood prop while the other is where a prop has been nicked by something striking it, be it either composite or wood. When the time comes to do the repairs, the procedure and instructions should be followed strictly to the letter. I mg of crushed baking soda with 2 ml of glue should be mixed in a tablespoon. Once the mixture is ready, apply the same immediately onto the damaged area. Fortunately for me, I found out that the propeller did not need any repairs. The Tiger Moth one-piece fixed wooden pitch propeller had no cracks and I only had to make sure that the wooden propeller was stored properly where there was no exposure of moisture. I only had to spray some paint on the newly installed Spitfire propeller that I had attached to the Tiger Moth and it is now ready for the exhibition. References Alfred, P, (1999), ‘How two brothers from Dayton added a new twist to airplane propulsion’ Mechanical. Engineering: 100 years Price, ‘Supermarine Spitfire, Griffon-engined variants and Seafire,’ Wings of Fame, Aerospace. Bransom, A, (1991), ‘The Tiger Moth Story, Fourth Edition. Shrewsbury,’ UK: Airlife Publishing Ltd. Price, A, (2002), ‘The Spitfire Story,’ Revised second edition. Enderby, Leicester, UK: Siverdale Books, John, W, (1983). ‘Janes All the Worlds Aircraft, London: Janes Publishing Company. Lovenitti, P, (2002), ‘A cost-effective thickness measurement technique for engine propellers,’ The International Journal of Advanced Manufacturing Technology. Karls, M, (1996). ‘Torsionally twisting propeller drive sleeve and adapter,’ Mario, T, (2001), ‘Great Maritime Inventions,’ Goose Lane Publishing. Bowers, P, (1979) ‘Curtiss Aircraft 1907-1947,’ London: Putnam & Company Ltd. Eltscher, L, (1998) ‘Curtiss-Wright – Greatness and Decline,’ New York: Twayne Publishers. Gunston, B, (2006).‘World Encyclopedia of Aero Engines,’ 5th Edition. Phoenix Mill, Gloucestershire, England, UK: Sutton Publishing Limited. Photos reference Movie Airplane! (1980). Box Office Data, News, Cast Information". The Numbers. www.bigfoto.com/themes/aviationwww (2000). mythicalireland.com/other/planes/index.php accessscience.com/content/Propeller-(aircraft)/548600 Take Care- Be Prop Aware, (2010). Campaign to Combat Propeller Injuries Yachte.com.au Mark Chapple and Martine Renilson,(2009). A Viable Approach to Propeller Safety for Small Craft: Ringed Propellers. First International, Symposium on Marine Propulsors (2009). Trondheim Norway. Reports on RingProp testing. www.fotosearch.com/photos-images/propeller-aircraft.html www.spitfirespares.com/spitfirespares.com/.../RFC%20Propellors.htm Read More