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#41
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"Koopas Ly" wrote in message
om... Climbout: same angle of climb for obstacle clearance at higher Vx speed. Almost. It should be the same *angle of attack* (and higher speed) for best angle of climb. But the angle of climb itself (and the pitch angle) will be less than when within max gross weight. Consider the limiting case where the aircraft is so heavy it can barely climb; the best angle of climb will then be just slightly above zero. Similarly, pilots who are not accustomed to high-altitude takeoffs can get in trouble if they try to set up the same pitch attitudes they're used to at lower altitudes for best-rate or best-angle climb. Due to the lower angle of climb at higher density altitudes, commanding the usual pitch altitude implies a higher angle of attack than usual, and hence a danger of stalling. --Gary |
#42
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In article , Greg Esres
wrote: Ah. I'm not sure how they determine Vo. They don't specify how it's to be calculated, and the Part 23 Flight Test guide doesn't say how to find it experimentally (unlike things like Vmc). What is the definition of Vo? I cannot find a definition of/for it. |
#43
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I've got an old Flying Magazine (circa 1970 or so) where one of the editors
makes the comment that it is better to take off overloaded (with fuel) than it is to try a launch with marginal fuel in order to stay under gross. The comment was the same... It'll fly better over gross than outta gas. I bet the magazine's lawyers wouldn't let them print that now... Don't tell anyone... but I did that almost routinely training for my PPL. We were flying an old, tired C-150 in a Georgia summer (which automatically means density altitudes are incredibly high). I weighed about 180 at the time; my instructor was about 240. We were usually over gross by about 40-50 lbs, and when flying dual we were lucky to get 250fpm out of it. My examiner was even bigger... I had to check the fuel levels and set it up so that I'd burn enough on the way over to his airport that we'd be right at gross for the checkride... which meant coming back home afterwards was cutting it close (but then, it's only an 11 mile flight). |
#44
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Gary,
Thank you for the correction. Everything you wrote makes sense. Could you please take a peak at my most recent thread entitled "Angle of climb at Vx and glide angle when "overweight": five questions". I added a clarification post in response to Mr. Gerry Caron's reply, within that thread, so I'd appreciate if you could tackle some of my questions. Thanks, Alex "Gary L. Drescher" wrote in message news:YBnxb.238322$ao4.855590@attbi_s51... "Koopas Ly" wrote in message om... Climbout: same angle of climb for obstacle clearance at higher Vx speed. Almost. It should be the same *angle of attack* (and higher speed) for best angle of climb. But the angle of climb itself (and the pitch angle) will be less than when within max gross weight. Consider the limiting case where the aircraft is so heavy it can barely climb; the best angle of climb will then be just slightly above zero. Similarly, pilots who are not accustomed to high-altitude takeoffs can get in trouble if they try to set up the same pitch attitudes they're used to at lower altitudes for best-rate or best-angle climb. Due to the lower angle of climb at higher density altitudes, commanding the usual pitch altitude implies a higher angle of attack than usual, and hence a danger of stalling. --Gary |
#45
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CJ,
My C172SP POH states that for short/soft field takeoffs with a 50-ft obstacle, flaps 10 should be used, as well as a climb speed of 56 kts until obstacle is cleared. Flaps should be retracted after obstacles are cleared after a safe flap retraction speed (what is that?) of 60 kts. is reached. Pitch for best angle of climb of 62 kts. after that during the enroute climb, should obstructions again need to be cleared. I am guessing that the 56 kts speed is best angle of climb speed for the flaps 10 configuration, even though that angle is probably less than the normal 62-knot best angle of climb clean, due to the parasitic drag induced by the flaps. From my interpretation of the POH (and the latter doesn't make it completely clear), if the runway was neither short nor soft, but with obstacles at the end, I wouldn't use any flaps, lift-off at normal speed, and pitch for the 62 kts. best angle of climb speed right away. Thanks for replying, Alex "C J Campbell" wrote in message ... | | Question (1 of 2): Seems to me that flying "overweight" is possible if | you're aware of the performance reductions. So why do you read so | many NTSB reports with probable causes listed as "overweight takeoff, | exceeded performance limitations"? As you slowly pull the yoke to | rotate, wouldn't a pilot *realize* through control forces, feel, gut | feeling that something is wrong? You would not necessarily feel heavier control forces if the airplane was trimmed properly. Heavier control forces as you rotate would indicate a forward cg, not over weight. You could be grossly over weight and have very light control forces if the weight was mostly in the back. Most noticeable is that the airplane does not accelerate as quickly as usual. If you are in the habit of flying overvweight, you might not notice anything wrong at all. Add in a hot day, short runway, and high altitude and suddenly you are going to find yourself bitten by bad habits. | | Question (2 of 2): When considering accidents due to exceeding maximum | takeoff weight, do the majority occur during takeoff? If so, is it | typically due to not reaching proper liftoff airspeed for that | increased weight, stalling, and spinning to the ground? Would this | scenario be consistent with failure to set the flaps/slats to their | takeoff value? Many airplanes take off from normal runways without flaps. A pilot can easily forget to set flaps for short or soft field takeoffs. A lot of pilots are also taught just 'plane' wrong. Consider the Cessna 172M, for example. Most pilots are taught to set the flaps at 10 degrees for a short field takeoff. Most aftermarket checklists tell you to do this, even the ones designed for older Cessnas. Surecheck sells checklists that are supposedly designed specifically for the 172M but they contain this error. But read the manual. It tells you that if you set the flaps at 10 degrees you will lift off the runway more quickly, but that you will climb more slowly and you might not clear an obstacle at the end of the runway. The manual says to use 10 degrees of flaps only when the runway is soft or is short but there are no obstacles on climbout. But the idea that you use 10 degrees of flaps to do a short field takeoff is so pervasive that I have had train my students in how to educate examiners on this issue. Newer Cessna 172s use 10 degrees of flaps for all short field takeoffs, so when transitioning from one model of Cessna 172 to another, be sure to read the manual thoroughly. |
#46
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"Bob Gardner" wrote in message news:0w5xb.234388$9E1.1274436@attbi_s52...
When considering takeoff parameters, don't forget the increased rolling resistance of overloaded tires...this will affect acceleration and takeoff distance. Bob Gardner Bob, Thanks for pointing that out. Never thought about the higher friction force between the tires and pavement due to the higher weight. Gracias for your continued contributions, Alex |
#48
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On Wed, 26 Nov 2003 10:18:14 -0500, "G.R. Patterson III"
wrote: Seems to me that you have listed most of the effects correctly. One thing you should consider, however, is the fact that the balance envelope for most (if not all) planes gets narrower at the top. In other words, the more weight you put in an aircraft, the closer to the center of lift that weight has to be. At some point, all of the weight will have to be in the front seat. Not really. You can put 50 pounds 3 feet in front of the zero cg datum and 50 pounds 3 feet behind the datum and it is the same as adding 100 pounds at the datum (front seats I guess). I have read of cross-Atlantic ferry flights in which the aircraft was loaded to weigh about 1.6 times the normal MGW. In one account, a Bonanza loaded that way took over 6,000' to get airborne. I let students take off at 2000 rpm in a 172. You roll a long way (very sensitive to temperature) and the climb performance is down right scary. George Patterson Mike Weller |
#49
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Mike Weller wrote: Not really. You can put 50 pounds 3 feet in front of the zero cg datum and 50 pounds 3 feet behind the datum and it is the same as adding 100 pounds at the datum (front seats I guess). That would be true enough, except that you can't put 50 pounds 3 feet in front of the zero cg point in most light singles. That would be where the engine is in my plane. George Patterson Some people think they hear a call to the priesthood when what they really hear is a tiny voice whispering "It's indoor work with no heavy lifting". |
#50
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(Rick Durden) wrote
In Alaska, Part 135 operators can get the max gross raised by up to 15%, depending on the airplane. Do you have a reference for this? You bet. 14CFR91.323 I've chased it a couple of times but can't find it (I'm assuming I'm looking in the wrong places); all I've found is for an increase for a few very old Dept of Commerce or CAA certified airplanes such as Stinson Trimotors and so forth, nothing modern. Really modern airplanes are not eligible for this, but a lot of stuff a whole lot newer than Trimotors is. If you've got a reference, I'd appreciate it. Here you go. A great web site for this stuff is http://www.access.gpo.gov/nara/cfr/c.../14tab_00.html 14CFR91.323 Increased maximum certificated weights for certain airplanes operated in Alaska. (a) Notwithstanding any other provision of the Federal Aviation Regulations, the Administrator will approve, as provided in this section, an increase in the maximum certificated weight of an airplane type certificated under Aeronautics Bulletin No. 7-A of the U.S. Department of Commerce dated January 1, 1931, as amended, or under the normal category of part 4a of the former Civil Air Regulations (14 CFR part 4a, 1964 ed.) if that airplane is operated in the State of Alaska by -- (1) A certificate holder conducting operations under part 121 or part 135 of this chapter; or (2) The U.S. Department of Interior in conducting its game and fish law enforcement activities or its management, fire detection, and fire suppression activities concerning public lands. (b) The maximum certificated weight approved under this section may not exceed -- (1) 12,500 pounds; (2) 115 percent of the maximum weight listed in the FAA aircraft specifications; (3) The weight at which the airplane meets the positive maneuvering load factor requirement for the normal category specified in §23.337 of this chapter; or (4) The weight at which the airplane meets the climb performance requirements under which it was type certificated. (c) In determining the maximum certificated weight, the Administrator considers the structural soundness of the airplane and the terrain to be traversed. (d) The maximum certificated weight determined under this section is added to the airplane's operation limitations and is identified as the maximum weight authorized for operations within the State of Alaska. [Doc. No. 18334, 54 FR 34308, Aug. 18, 1989; Amdt. 91-211, 54 FR 41211, Oct. 5, 1989, as amended by Amdt. 91-253, 62 FR 13253, Mar. 19, 1997] |
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