Safety first! If you are not thinking about safety before, during, and after going flying, this is not the hobby for you. There are quite a few people out there who are great builders. These folks would never think of building anything without thinking it through carefully. Put them in their creations, however, and the rules change. Suddenly either their plane is a fighter, complete with unlimited thrust and no g limits, or they possess the skill to do any maneuver they heard someone once did in their type aircraft. The statistics prove these are bad ideas. Before doing something in an aircraft that sounds cool, have you thought out the risks? Have you rehearsed it in your mind? Do you have a back-up plan? Do you have a busted maneuver plan? The words "its no big deal" rank right up there with "watch this!" as the most common things last heard before a mishap. Things to STRONGLY consider from the safety perspective before doing anything out of the ordinary include: - Low level flights (below 500 ft AGL): Engine failure: Is there a road or field close enough to get to? Is the radio on a frequency a mayday call may be heard? Bird strike: What happens after hitting a large bird? If it takes out the engine? If it penetrates the canopy? If it hits you in the face? I have friends who have experienced all three in jets. A 1/4-inch thick canopy will not stop anything larger than a pigeon. Not sure this is true? Talk to someone covered in hawk or owl goo that came through a reinforced military windscreen. Wires: Has the route been scouted for hazards? Is it verified (by the pilot) there are no power lines, guy wires, or cables in the vicinity? Other aircraft: If the area is too cool to pass up others know about it as well. - Aerobatics Have you received training? What are the airframe's real g-limits? Can all maneuvers be completed within the g-limits? Busted maneuver - What is the plan for extreme nose down/nose up/inverted/zero airspeed/high airspeed recovery? Flight controls - Can the maneuver be completed in a reasonable amount of time? Do the flight controls have sufficient authority to control the aircraft at low speed? What are the loss of control, stall, and spin recovery procedures for the aircraft? FOD check. Is everything in the entire airplane strapped down? Is FOD in the cockpit going to be an issue at zero or negative g? Better believe it. G-loads Are you able to handle 4-gs without graying out? Have you flown in this regime with a safety pilot to verify your answer? G-tolerance is extremely perishable. When was the last g flight flown? Outside of two weeks, plan to take a warm-up flight to reacquaint your body to the strain. Do you know how to recover if you start to gray or black out due to g-loc? Before doing any high g maneuvers, do a g warm to ensure you are ready to begin maneuvering. Military aircraft are not permitted to engage in high g combat training without doing a g warm. The typical (military) g warm consists of a 90 degree turn at 4-g, followed by a 90 degree turn at 6-g, then a zero g bunt or inverted flight to check for FOD. This is for aircraft with 7.5-9+ g available. Modify as required for the g expected during your aerobatic flight. - P-factor/engine stress Is the engine/prop combination able to handle the loads of maneuvers? Maneuvering can include high g turns, aerobatics, or rapid/sharp control inputs. Will the cumulative effect of maneuvering exceed the limits of the engine? Corvair engines have flown for decades without problems. In the past three of four years this engine has seen numerous crank failures. It cannot be ruled out that these engines were overstressed by demands placed upon them by their pilots. - Formation flying Formation flying is a lot of fun. It is also not something the average pilot has a great deal of experience in. The FAA requires a face to face brief between PICs. If flying close form NEVER TAKE YOUR EYES OFF THE OTHER AIRCRAFT! Keep your distance. While flying close to another aircraft sounds neat, things can happen very fast as that distance. Control your closure during join-ups. Do not lose sight during a join-up. As lead, remain predictable. No sudden maneuvers. If you swap paint, the formation flying is over for the day. Get separation, keep sight, assess your controlability and land. I flew "unlimited" planes for 20 years. Truth is, none of them were truly unlimited. Doing stupid things in the air eventually leads to a smoking hole in the ground. ALWAYS HAVE A WAY OUT! Always brief or review what will occur during a flight, including emergencies. Some statistics from AOPA's 2007 Nall report on homebuilts: Evolution / % Mishaps / % Fatal Preflight/taxi / 3.2% / 2.5% Takeoff/climb / 22.2% / 17.5% Fuel management / 6.3% / 2.5% Weather / 1.6% / 5% Other/cruise / 1.6% / 5% Descent/approach / 6.3% / 10% Go around / 1.6% / 0% Maneuvering / 16.7% / 40% Landing / 38.1% / 10% Other / 2.4% / 7.5% 33% of fatal accidents in single engine fixed-gear aircraft (non-homebuilt) were attributable to aerobatics. The takeaway from these numbers is to not be out doing things in an aircraft without training and experience. There are plenty of pilots out there who will never do anything in an aircraft that might be called "maneuvering". When one in six mishaps are related to maneuvering and two in five of those result in fatalities, it does not take an advanced degree to understand a disproportionate number of pilots doing aerobatics are exceeding their skill level or the limits of their aircraft and paying the price for it. Weather Turbulence: It is a true statement that we all learn from mistakes. Some of those mistakes really should not have happened in the first place. Take for instance my flying through a SIGMET for turbulence a few years ago. The weather called for an AIRMET over SOCAL for moderate turbulence and a SIGMET for occasional severe mechanical turbulence over the LA Basin. Feeling the pressure to get my plane from San Diego back to Fallon, NV, I took off anyway, reasoning that if I ran into something I did not like it would be no big deal to just turn and land. The air was bumpy as forecast, right up until I was ten miles south of Tejon Pass. One instant I was flying along at 6500 feet, the next I was five hundred feet higher. The updraft was so strong I could not even see the instruments, and my g-meter hit almost 4.0 g in that instant. There would be no turning back, because I was not going to voluntarily fly through that again. So, with the only way through being to press over the pass, I hunkered down and tightened my seatbelt. Three miles from the top of the pass I got another extreme jolt upward. During both events the plane was completely out of my control. Not good. Really stupid. The rest of the flight over mountains I was completely on edge, waiting to get slammed around again, even when I was out of the SIGMET. Light: Slight erratic changes in attitude or altitude. In the KR this typically starts as yaw. A bit stronger and it affects roll. Easy to control without much thought. A word about Va airspeed and severe turbulence. Flying Va DOES NOT GUARANTEE your wings or tail will no peel off the airplane in severe turbulence. If you are flying below the weight at which Va was derived the maximum g your airframe can operate at without damage is less than 3.8. The formula for calculating Va is simple: for Goliath this works out to: In reality the Va is probably a bit lower, as the true stall speed is probably around 68 if I were flying really smoothly at stall. What happens if I am flying 150 pounds lighter than this and my stall speed is now ~65? That is a 10 MPH IAS difference, or a 7% difference in potential load capability. I personally fly a bit below Va in moderate turbulence because if my airspeed indicator is off a bit it is probably showing me flying slower than I actually am. Personal opinion. General Aircraft Performance - Takeoff: Weight: Takeoff distance is a squared function of gross weight.
The effect of wind is not quite as mathematically exact as weight. Based on the takeoff speed, the RATIO of wind velocity to takeoff distance is: 30% tailwind - 168% Normal takeoff distance - Climbout: More weight = more lift needed = more drag = more power required -Enroute: As weight increases, the speed needed to fly a max range profile increases
- Landing: The charts that work for takeoff WRT wind apply to landing as well. By the same token, landing with extra speed is equivalent to tailwind, i.e. Landing with 10% more speed than needed will increase the landing rollout to 121% of normal. Example: Tire pressure is 40 PSI = 9 * SQRT 40 |
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Important things to know |