Pitch Of Aircraft - Next, you must establish the maximum propeller diameter your airplane can accommodate. Determine this with the aircraft in a level (take-off) attitude. Measure the distance from the crankshaft to the ground and subtract 9 inches to allow for safe ground clearance. For example, if the hub-to-ground measurement is 45 inches, subtracting 9 inches will leave an effective radius of 36 inches. This limits your maximum allowable propeller diameter to 72 inches (36" x 2" = 72"). Incidentally, if you are the proud owner of a nose gear equipped aircraft, you have another concern. In the event the nose gear shock strut collapses, or the tire goes flat, will the remaining ground clearance (allow 2" to 3") be sufficient to save the prop?
We tried slimline seats out recently in Germany, and were impressed -- although in fairness that's because Lufthansa decided to split the difference with passengers. The airline gets more seats on the plane, and passengers get a bit more legroom.
Pitch Of Aircraft
In short, if you can't obtain the recommended minimum static rpm DON'T TRY TO TAKE OFF WITH THAT PROP . . . especially from a short runway! This caution is especially applicable for low power, direct drive VW engines that turn at a much higher rpm than standard aircraft engines. That 2900 rpm sounds high compared to a certificated aircraft engine but don't be fooled. Play it safe!
The Axis Of Aircraft – The Quick Definition
(In fact, interesting aside: I first decided to write this article because I was fed up of saying "that's the space between your seatback and the back of the seat in front of you, not counting the tray table -- in other words, what you can call your personal space on a plane".)
At this point the representative aircraft shown in Figure I may or may not be considered as particularly helpful. After all, how many homebuilt are as large as the Piper Cub or are like the Ercoupe? I guess this is exactly where the problem really shows. The size of the homebuilts, their weight, and their (generally) lower drag characteristics, certainly, are different from the larger store boughts.
START WITH YOUR ENGINE Our discussion will be on the fixed pitch propeller problem only. The type engine you have installed will dictate the basic propeller approved for it. The engine manufacturer has established for you the authorized maximum and minimum propeller diameter and pitch permitted. If you rely on this information alone, you will not get into any serious trouble. At worst, your bird may be a bit sick in its performance, but at least it should fly well enough to keep you safely airborne.
Static RPM Is Important A static rpm check is the best assurance you can have that your engine can handle the installed propeller. Perform your static rpm check by starting the engine and accelerating it smoothly up to full throttle (no wind condition and wheels chocked, of course). The engine should be able to reach approximately 80% to 85% of its rated (redline) rpm. A minimum static rpm has been established for each aircraft engine.
Up To Bonus Qantas Points - Westpac Altitude Black
Getting Off The Horns Of The Dilemma What does all this mean? What if you don't get the hoped for rpm during the different performance checks? If your engine doesn't reach the desired rpm, your propeller pitch is too high and/or the propeller diameter is too large. You are most likely overtorquing your engine.
However, aircraft designers generally aim to make aircraft behave predictably. So, they engineer the aircraft so that the aircraft axis (or skewers, if you prefer) runs through a certain point. And this point is always the same, regardless of aircraft weight.
Having said that (and maybe it is already part of the site refresh coming soon) it could be helpful to have a seperate directory on AUSBT which lists topics and has links to relevant post from the past. Esp on the seatpitch, lie flat / full flat, airline alliances, airline lounge topics (I am aware you kind of have his in the left hand menu when you click an article / on the bottom of the page) but I am talking more an "at a glance" or "Common airline lingo explained" section.
We make a gentle push on the left rudder pedal. In the simplest terms, this will cause a rotation around the vertical axis. The longitudinal and lateral axes will move in the direction we push on the rudder pedals.
Final Thoughts
Propeller manufacturers have listings of their propellers. These listings show the propeller models available for different engine/aircraft combinations. In addition to the diameter, the recommended standard, cruise, takeoff and climb pitch is also given for the different aircraft using a particular propeller. A considerable amount of work and research made possible the information shown in Figure 1. It can be used as a quick reference by anyone who has yet to determine what propeller his engine can handle. With this information in hand you can then start your search for the right model prop. Unfortunately, time did not permit a broader report to include other excellent propellers on the market.
Who Has A Prop You Can Try? Do you or a fellow builder own a spare propeller that you could try? If so, first find out whether that propeller hub will fit your engine. Lycoming engine flanges are not the same as those on Continental engines. Then, too, propeller bolt hole sizes vary. Naturally, Volkswagen engines have still another bolt pattern and the same can be said of other engine conversions. Anyhow, if the prop hub fits your engine, fine. Why not give it a try. I assume that you will have plenty of ground clearance. And how about weight and balance? Can you accept the weight of a metal prop - assuming it is metal?
TheRealBabushka: lighten up dude. Not only is AusBT not just a 'news' site as John said, with lots of articles for general reference and information, but the guys were at Sydney Airport yesterday morning, Sunday, to cover the new QF A330 when most of us were in bed or having breakfast. I don't think you can then take a shot at them as if they're lazy!
The metal propellers installed were hand-me-down types off of wrecked or canabalized aircraft, or, at best, were "serviceable" used propellers. It is true that some of them had gone through authorized prop shops and were properly reconditioned. A good number of them, however, were cut down to salvage a bent prop. A few "prop sources" around the country are advertising props as "suitable for a homebuilt". Is that so? What it means is that they have a damaged prop which was probably cut down and refinished. It can no longer be used legally on a store bought aircraft so why not sell it to the homebuilders . . . they will use anything. Well, from some of the propeller accident reports I've read about, it may be true. Not sensible, but true.
A rule of thumb has it that when you decrease the propeller diameter by one inch, or decrease the pitch by one inch, the rpm will increase by about 50 to 100 rpm . . . say, on the average, 80 rpm.
Some airlines sell seats with more legroom than that for an extra fee. On smaller planes like Boeing 737 or Airbus A320 jets, these might be the front row, a bulkhead or an emergency exit row.
If your airplane is a popular one, there are probably a number of them already built and flying. Ask their owners what size prop they are using. If possible, compare the results as reported by them and form your own conclusions. Remember, though, that some of these gents may not really have accurate data to give you. Accept the information with the same reservations you may have in accepting your neighbors’ claim of gas mileage for his new car.
Well, how about buying a new certificated wood propeller? A FAA approved wood prop (suitable for most certificated light aircraft) does have a somewhat more sane price tag - it costs only half as much as a metal propeller. It also has less than half the weight of a metal prop. This could be an important weight and balance consideration.
What'll it be? $400 for a homebuilt custom-made wood prop, $600 for a certificated wood prop, or $1500 for a certificated metal propeller? With prices like that, it is essential to make the correct initial choice unless you want to join the increasing number of builders who are becoming involuntary collectors of mismatched propellers.
The calculations are a little different in the angled lie-flat seats and fully flat beds of long-haul international business and first classes. (Qantas occasionally runs this type of seat between Sydney and Perth on Boeing 747 and Airbus A330 planes too.)
There are three axes around which all aircraft move. The aircraft moves around the lateral axis in pitch, the vertical axis in yaw, and the longitudinal axis in a roll. By combining the various rotations of the aircraft around all these axes, the aircraft can maneuver into an attitude.
How About Buying A Used Metal Propeller? You can, of course, buy a used propeller if you are willing to take the risk. The risk is greatest in buying a used metal propeller having an unknown history. You have no way of knowing if that propeller has been severely damaged and the tips straightened; or if the blades have been damaged that the damage was minor and within authorized repairable limits. There is always the possibility that someone may have straightened them a bit before taking the prop to a propeller shop for repair and rework. A reputable propeller repair shop will not knowingly rework a propeller that is bent beyond authorized repair limits, but they too can be fooled sometimes.
The McCauley Industrial Corporation has offered the advice that all of the EAA people should be encouraged to use a propeller within the diameter range that is approved vibration-wise on the engine. Too many of them, they said, are using short diameters on 4-cylinder engines which may get them into trouble.
But even some homebuilders are playing the same game with themselves as the target. They have a damaged prop, and it will fit the hub. And then the obvious thought that it must be cut down to salvage it. He does so, and winds up with a smaller than desired diameter propeller so, as the final step, he has a bunch of pitch cranked into it. According to his incomplete and faulty reasoning the airplane will be faster . . . but even if that were so . . . what about his prop . . . his engine? How long will the prop last? How long can the engine operate above the recommended maximum redline rpm authorized by the manufacturer?
In the case of pitch, the aircraft rotates around the lateral axis. But the nose and tail move up and down. Nose and tail? That rings a bell! The axis running through these points is the longitudinal axis. So, while the rotation point is around the lateral axis, we call the rotation longitudinal control.
Nevertheless, I don't believe that there is a flagrant or deliberate intent by the homebuilder to disregard the engineering guidance available regarding the propellers/engine/airplane match. How come, then the situation that we have? An informal check of my own showed, that of the many projects I checked, NOT ONE was equipped with a new metal propeller . . .
On many aircraft, the horizontal stabilizer and elevator create a symmetric airfoil like the one shown on the left of the shape effects slide. This produces no lift when the elevator is aligned with the stabilizer and allows the combination to produce either positive or negative lift, depending on the deflection of the elevator. On many fighter planes, in order to meet their high maneuvering requirements, the stabilizer and elevator are combined into one large moving surface called a stabilator. The change in force is created by changing the inclination of the entire surface, not by changing its effective shape.
On the other hand, there is this concern. If the recommended static rpm cannot be reached, it indicates that your engine is overtorqued (overloaded). In effect that means that your propeller diameter is too large, or that the pitch is too much, or both. This condition is detrimental to the engine if allowed to continue. Not only that, it is also fair warning that your propeller will not allow the engine to develop sufficient horsepower for a safe take-off!
You should check your engine and both instruments if you want to tweak the best performance possible out of your propeller. Use a Reed Tachometer or a Tach Chek to calibrate the tachometer. I am sure you can see that a slow indicating tachometer and/or a high reading airspeed indicator could really fool you by concealing the fact that your airplane is somewhat slower than the numbers would indicate. Conversely, it would be nice to learn that your airplane is really faster than either the tachometer or airspeed gage would have you believe.
YOUR AIRPLANE IS just about finished and you do not yet have a propeller for it. Joe down the street has a good metal prop but the tips are curled from a taxiing accident. Joe doesn't know what aircraft it came from but he realizes he won't need one himself for a couple of years, so he will let you have it pretty cheap. The offer is tempting for you have just found out what the prices are for new metal props. The money you have set aside may not be enough for a new propeller. Even if it were, can you afford to pay a big price for a new propeller, which may not be exactly right for your bird? What to do?
Pitch is still important at the pointy end of the plane, though: the more space there is in front of you, the easier it is for window passengers to nip out over a sleeping aisle passenger.
But, John what I'd really love to learn (and have analysed for me) is the application of EU regulations for airlines and its impact on carriers/pax within and without the EU. What are reach and limits of these regulations?
Maybe you won't get the perfect propeller for your bird on the first try, but if you approach your problem with logical reasoning, you will at least have eliminated a gross mismatch in your selection process.
One more word on propeller diameter. Have you ever heard of this one? "Keep your prop as long as possible as long as possible!" I'll give you one good argument for longer prop diameters. Next time you get near a nice homebuilt with a beautifully cowled engine . . . just check and see how much of the propeller area is blanketed out by the engine cowl when the prop is in the horizontal position.
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