“Ladies and Gentlemen, this is your Qantas captain speaking. We will commence our descent into Los Angeles in 5 minutes. I thought I would take this opportunity to inform you off yesterday’s US election results. … surprising swings in Florida, Pennsylvania … The president elect has been declared to be Donald Trump.” Hmmm, this trip to the US is becoming more interesting that I anticipated.
This begs the question of why have I spent 28 hours travelling from Perth to the US the day after their rather fraught election and spending 5 days recovering from jet lag in a Las Vegas casino resort? The answer, of course, is to attend a course on Twin Cessna piston aircraft systems and engines. Why else would anyone go to Las Vegas?
I am a previous (as in 30 years ago) owner of a Twin Cessna (specifically, a turbo Cessna Skymaster 337 “suck and puff”, not quite considered to be a “real” Twin Cessna). I have returned to aviation with the hope and intent of getting a “real” Twin Cessna. My RACWA instructors and examiners have been noting my efforts to re-acquire flying skills with patience and sometimes bemusement, but here I am with a fresh Aussie multi-engine rating to compliment my antique-status US FAA license. So, the barnacles have been mostly removed from my flying skills and it is now time to look at planes. This has brought me to Las Vegas (Please don’t tell my Colorado-based mother this. She thinks I planned to visit her in Denver and then found a course to attend, not the other way around).
The course is set at the Henderson Executive Airport in South Las Vegas. Thankfully our classroom overlooks the side away from the runway, or I’d find the endless queue of bizjets a distraction. I do remind myself that “true pilots fly props, not vacuum cleaners”. My first impression is the age of the pilots attending. Hmmmm. Yes, there are some Millennial mechanics attending but the majority of the pilots are in their 50’s or are 60+. I am part of the antique group, having been born just as the first twin Cessna (a 310) was sold to the public. This may a case of anachronisms flying anachronisms. This is further reinforced by the opening remark, “We are in restoration mode, not maintenance mode.” I suspect this was meant to refer to Twin Cessnas: It may also refer to my knees.
That opening statement was made by Bob Thomason, who runs the Twin Cessna Fliers organisation. What a great group of fliers and restoration experts. Bob commercially flew his own Cessna 421C, the “Golden Eagle” and now flies a Cessna 303 for personal use. His passion, enthusiasm, attention to detail, and desire to educate is contagious. I recommend that anyone who wants to fly or own a specific plane type consider joining whatever organisation supports the particular plane’s enthusiasts/owners. If it is anything like Twin Cessna Fliers, then the financial return and satisfaction of ownership/flying is repaid multiple times. It is also an excuse to talk to more pilots about flying and planes – definitely a “win-win”.
After the formalities and introductions are completed, it is over to Tony Saxton, our erstwhile instructor. Tony may be yet another anachronism maintaining anachronisms, but he is a pretty impressive one. Tony spent his earlier years running a business in the NE USA (the “known icing capital of the world”) flying Twin Cessnas as freighters. They hauled cancelled cheques for the US Federal Reserve bank (Millennials: Cheques are old-fashioned financial instruments that were sometimes filled in with typewriters, but we don’t use them in Australia any more. Ask you mother or grandmother what life with cheques – or typewriters – was like). He now runs one of the largest maintenance facilities in the US focusing on Twin Cessnas, and is pretty much the go-to guru for everyone, including the FAA, for Twin Cessnas. He was the FAA Maintenance Technician of the Year in 1993, so the FAA thinks he knows his stuff. Tony spends a fair amount of his time explaining to the FAA how their proposed Airworthiness Directives (AD’s) don’t quite work on all models and why. Tony is rather understated with his expertise, so I can only conclude in our “post-fact world” that Tony is a gem and can be trusted in both his factual knowledge and his conclusions. Others think so too. One of the C-421 Golden Eagles for sale on Controller.com advertises that the current owner has attended this course as a key selling point.
Like all good meaty aviation seminars, we immediately get right into the accident statistics. Non-aviators clearly don’t understand the tendency pilots have to study failure, but I love it. There are a few surprises in what causes prangs, which I somewhat oddly find comforting, but I’ll summarise key points at the end. After accidents, we get right into Regulations and Documents. As an engineer, I agree that getting into the rules, design bases and means of proving how these are obeyed is of paramount importance. Reading the Type Certificate Data Sheets is educational and helpful, if not exactly spell-binding literature. I can only suggest that our Millennial students read the TCDS for a C-152, then go ask Glenn a question or two about it. You may want to have the RFDS in attendance as he is likely to fall off his chair.
Onto the airframe metal, which in aircraft inevitably leads to an in-depth discussion on corrosion. Yes, our aircraft were originally part of The Pilbara and inevitably willl return to base metal rock there. We cannot eliminate corrosion, but can at best manage its rate of progress. This is best done with a large bank account but some common-sense procedures help. Fly the plane fast and often, then spend the time saved by carefully cleaning the plane, seems to be a good dictum.
We then delve into FAA Advisory Circular AC-43-4A, titled Corrosion Control for Aircraft. This document is a gem, despite being published by a governmental body. Yes, they did manage to mis-spell the name of an apparently-minor Australian city as “Sidney”, but we know that just confirms it was written by genuine Americans. The Curcular shows how to check, minimise and eliminate corrosion, gauge its impact and how to fix it (if Glenn were to see any Millennial reading or implementing this document, oxygen may be required). There is a chart in AC-43-4A which is helpful in setting my own expectation. It shows corrosion levels at worldwide locations. Most of the US is “Mild” with pretty much only Florida and Mississippi showing “Extreme”. My birth place of Colorado is “Mild” (almost “Non-Issue” I should think as nothing rusts there). Alas, most of the places in Australia where we base and fly planes is “Extreme” – the same as Papua New Guinea. Having worked in PNG and seen what 15 m/yr rainfall is like, I personally think it ought to be “Catastrophic” but the chart doesn’t go that high.
Okay, the Fremantle Doctor currently whistling through my study is full of salt, which accelerates corrosion. I guess this helps justify the astoundingly-expensive Cessna SIDs programme required by CASA, which requires wing root inspections, amongst other things. This has just been completed on the RACWA C-152 fleet and no doubt has impacted on rising flight hourly rates. Americans don’t have to do SIDs on privately-owned planes, as their corrosion rates are lower and the US is a much easier and less expensive place to safely hangar planes than are our investment bank-owned airports here in Perth. Tony shows a few photos of corrosion, which makes me kind of glad to pay for the SIDs inspections and know the wings will remain attached. Being below freezing may reduce the US’s corrosion rates, but I would rather pay for corrosion-related repairs and not have to brush snow off of wings with numb hands for 6 months of the year, like I did in Colorado.
After an “airport standard” lunch of burgers, salad and iced tea, we’re into specific systems. Electrical is the first subject followed by Environmental Systems (Heat, Cooling, Pressurisation). Given the last Twin Cessna was built in 1984, it is a sure thing that all of them have been modified, changed, upgraded, or fixed any number of times. Key points I want to remember include that (a) voltage is measured on the busbar voltage, not the battery’s voltage; (b) using the external plug to jump start a Twin Cessna can reasonably lead to complete electrical failure just as the landing gear is ½ way retracted; (c) battery boxes are located in the wings in a perfect location for any spilled battery acid to start dissolving wing spars, and (d) heaters are an endless source of frustration and if “not maintained in strict accordance with ….” can cause an attention-getting explosion just in front of the pilot. On the positive side, once pilots and passengers stopped smoking in these planes, the pressurisation systems stopped having problems. Pressurisation system components pretty much take care of themselves when in smoke-free air.
The morning of the second day lands us (aviation joke) on an appropriate subject – landing gear. This subject causes long-term Twin Cessna owners to get highly animated. It is obvious that landing gear is the source of lots of angst and financial pain to the owner group. Most of the Twin Cessnas have electro-mechanical gear which uses long skinny rods to prod the gear into the desired condition. They don’t stay in calibration for long and pretty much any problem results in jammed gear, if not caught by complex inspections. Tony’s mantra is to have mechanical gear completely re-rigged at every 100 hour, which takes about 8 man-hours by someone who does this a lot. In one of those oddities of aviation, the latest models of the most complex, capable, and sophisticated Twin Cessnas (the 414A Chancellor and the 421C Golden Eagle) have hydraulic gear. This gear is simpler, more reliable and retracts/extends in half the time of the mechanical gear. If the hydraulic gear does break it is “very expensive” to repair.
Next is fuel systems. On all but the more sophisticated C-414A and C-421C models, the fuel system is complex and prone to problems related to quiet engines. The C-414A and C-421C models have larger “wet wing” tanks that are pretty much set and forget operations. The early ones have a multiple of smaller tanks that supply fuel in inconsistent ways and have up to 8 fuel pumps in them. In other words, they are a fluid system that only a Chemical Engineer could love (yes, I’m a Chemical Engineer). The change to low-lead fuels, which contain a lot of naphtha (a substance only Chemical Engineers can love) causes more problems. Naphtha dissolves rubber bladders, seals and causes fuel selectors to not quite work as desired. This is nothing that a lot of training, maintenance and money can’t overcome. There was a long, detailed discussion about removing water from fuel, managing ice crystals in fuel, and how to check for jet fuel (vs 100LL avfuel) being filled into tanks by 18 year old linemen on minimum wage. Luckily these problems don’t generally occur in Perth like they do in the US. We have to have a few things go our way to make flying easier here!
The final two days of the course focused on engines, props, and things attached to engines. The first few hours are less-than-encouraging. We learn how these engines can fail, they flex a lot when operating, they are at the design limit of size for opposed-cylinder designs, and lots of the failures are caused by pilots with rusty skills. I’d better pay close attention here.
The engines on Twin Cessnas are large-bore, 6 cylinder engines manufactured by Teledyne Continental (now just Continental Motors). The initial discussion was on nomenclature and general layout of the different engine models. This started out as a rather dry subject, but then it became apparent that with modern engine monitors, there have been a lot of instances where the pilot says, “Number 6 cylinder is running rough.” Only later, much later, does the mechanic learn that the pilot’s #6 cylinder is really #2. Nomenclature errors can be expensive, painful and rather embarrassing.
We then proceed to how these engines work and fail. This of course leads to the subject of cooling the engines and causes of detonation. They are cooled by air (yes, they are called “air cooled” for a reason), lubricating oil, sometimes water (very rare now), but most importantly fuel. Water cooling works wonderfully and there are a few C-414s about with water-cooled engines. The big problem was the weight of the water systems, never mind the cost of an overhauled water-cooled engine being twice the cost of a comparable air-cooled version.
All big bore Continental engines are set up to run quite rich (ie, more fuel than can be combusted by the available air) at high power settings. This rich setting cools the engine when fuel evaporates upon injection. Rich fuel also slows flame speeds and reduces peak firing pressures, which prevents dreaded detonation. Most of these turbo engines are happy to remain set at full power all the way to cruise altitude, providing the mixture remains fully rich. This might be a challenge when departing Jandakot while Perth Approach is busy.
Ignition systems were covered in some detail. I realised that my engineering skills were less helpful here than having driven a Model A car in my youth (Millennials, ask your great-grandmother what a Model A is). The Model A used magnetos to generate sparks, but they manually retarded the spark when starting. Same magneto systems as on sophisticated Cessna Golden Eagles. Spark plugs were discussed as well. It seems the problem with spark plugs is manufacturing quality control related more than anything else. I guess people tend to buy the cheapest spark plugs, which has led to some interesting problems with bits falling off plugs or bad firing properties. The dominant view of those who owned Twin Cessnas is that fine wire spark plugs were better than the massive plugs in turbocharged engines.
The physics of ignition systems makes it inevitable that air is an insulator and lack of air (ie, high altitude) can lead to low air pressure in the magneto, causing sparks in the magneto instead of in the desired engine cylinder. This is not good, not good at all.
The large-bore Continental engines aren’t really designed to put up with ignition-related problems. Indeed, the most complex version, the geared, higher-speed GTSIO-520 (on the Golden Eagle) is required to undergo a teardown inspection if it ever experiences any roughness that requires movement of throttle/prop/mix controls to clear the roughness. I don’t even want to think about what this might cost.
Oil systems started the final day’s discussions. Suffice it to say that these engines were designed for a certain oil specification and it should be followed closely. Using additives or trying to find other means of extending oil life leads to expensive repairs later. Should the engines be laid up for even a month or so, then oil changes need to happen earlier to keep these engines working as designed.
If the fuel storage systems are overly-complex, then the fuel injection system is the runner-up on the complexity scale. They have to get fuel than can have vapour in it controllably flowing into temperamental engines – all with equipment designed before computer flow and pressure controls. It is amazing that these engines have any reliability at all. Turbocharging these engines is more likely to cause a problem, and the problem causes more damage quicker. Turbocharging does provide pressurisation and flights above the weather, which makes the fun factor increase in parallel to the cost factor.
If there is any part of the power systems that truly amazed me, it is the engine mounts. On Twin Cessnas, these are not the welded tube design we see on most single-engine planes. They are made of Aluminium sheet similar to what is used on wings. They are carefully folded, formed and fastened together then attached to the wings. What is amazing to me is that they weigh only 2-3kg but can support a 250kg+ engine/prop and all the forces exerted on, and by, these engines. Of course, with any design there are compromises and the compromises of Twin Cessna engine mount design are resilience and durability. Any little bit of wear or damage and the wing is disassembled to replace the engine mount. It seems that the item on Twin Cessnas designed to damage engine mounts the most is control cables (throttles, mixture, cowl flaps). Cables anywhere close to the engine mounts can rub “just a little bit” on the mounts and cause them to fail inspection. Examine cables closely whenever oil is changed or be prepared to spend a fortune on replacing engine mounts. I suspect staring intently at an engine mount can cause it to crack and fail inspection.
Exhaust gas is also something that can quickly damage engine mounts. The littlest exhaust leak of a turbocharged engine can quickly melt an engine mount or cause it to fail. Ouch! In addition, exhaust systems on these planes are prone to cracking or melting as they see extreme temperatures (they glow yellow-hot when leaned for cruise but are cooler at max power or approach), are thin, vibrate and are packed close to controls, fuel lines, fire walls close to fuel tanks and other interesting combinations. Nearly all Twin Cessna exhausts require a careful inspection every 50 hours. Trying to short cut these inspections does not make for good flights.
Despite all the compromises inherent in the design of Twin Cessnas, I absolutely adore their capabilities and look forward to owning one in the (hopefully) near future. The twin benefits of the Twin Cessna course (bad aviation joke) is that it will hopefully make my ownership/flying of these amazing but old aircraft more satisfying, and cheaper. The course has also set my expectations of the costs, problems and down time at a realistic level – hopefully my wife will feel the same after a year or two. Watch this space.
The course was satisfying, enjoyable and more helpful than I expected. There was one disappointment at the end. I had hoped that one of the attendees would be flying easterly after the course in their Twin Cessna and I could cop a ride towards Colorado. Alas, those that flew themselves came from California, Oregon or Arizona – not the right direction. It was back to American Airlines and long security lines. Oh well, into each life must fall some disappointment.
Conclusions and Key Points
- A Twin Cessna Fliers member made an informal study which showed that 38% of all accidents had Systems Failure as their origin (including not maintaining/operating as per design). This is strangely reassuring to this engineer but rather rusty pilot, as I like studying systems.
- Corrosion is inevitable and will inevitably cost more each year to control. It is a race to see which corrodes into oblivion first – the last Twin Cessna or the last Twin Cessna pilot.
- In Perth, we live in an environment highly-corrosive to aircraft – it is a part of the warmth, sun and sea lifestyle. At least we don’t have to bother with much ice or birds that think plane cavities should be their new family home.
- The first test flight of a Cessna 340 ended up killing Cessna’s test pilot. The cause was the little bolt attaching the trim tab to the elevator working free, which caused the elevator to flutter then jam. This led to an inverted flat spin. The littlest bits on a plane can cause the worst accidents. Inspect them carefully on each pre-flight.
- Electrical systems may not have many moving parts, but like aged nerves and veins in 50+ yr old pilots, brittle wiring is expensive and painful to replace, but it must be done.
- Mechanical landing gear is costly to test but (relatively) easy to fix.
Hydraulic landing gear is easy to test but (extremely) expensive to fix. Make your choice and spin the wheel. This is Las Vegas. - Bent fenders on front wheels and any dent on the steering stops of Twin Cessnas lead to bad gear problems. Of course, all gear problems are bad.
- Learn how to lubricate properly, be it wheel bearings, turbochargers, bolts, cables, or mechanics. You’ll be a much happier, richer, and safer pilot.
- Always use full power and max richness when taking off with turbo Twin Cessnas. This prevents leaner mixtures causing detonation or overheating – and makes take-offs more fun.
- After annual/100 hr inspections, new engine installs or whenever anything on the engine is changed, do a series of test flights to record all sorts of engine parameter data. Not only does this provide a valuable source of “baseline” data for when there is a problem, but it also justifies more flying.
- In discussions with the other pilots during meals, it became apparent that the rigour and consistency of training we experience at RACWA is closer to what US military pilots undergo than what generally occurs at civilian US airports. Respect is due to Trevor, Amy, and the RACWA managers who drag their students up the competency path. It makes for better aviators and is ultimately worth the pain and cost!
- In 1975, a hapless Aussie exchange student arrived in Denver 2 days after I gained my private license. She was my first passenger. She only remembers trying to avoid getting sick in a claustrophobic, hot C-150, but it must not have been too bad. She and I have been married for 35 years now, and she is my biggest source of encouragement to get another Twin Cessna. I suggest that it is better to get the aviation bug first and then pick a life partner who is sympathetic to the aviation bug vs the other way around. I timed that right by 2 days. PS She no longer gets sick when we fly.
Article Written by Jim Dowell
