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#21
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Mike Rapoport wrote:
wrote in message ... Mike Rapoport wrote: : Keep in mind that the short field settings shorten the ground run but : generally increase the distance to clear a 50' obstical. Isn't that the *point* of short field technique... to get off and over in the shortest distance? There would appear to be a logical flaw to that statement. I would agree that it will take more *time* to get to a given altitude at (e.g. 50' obstacle clearance)... Short field performance is defined to give the best obstacle clearance per *distance*. I would agree that soft-field technique will increase distance, but short is short. Am I missing something? Maybe :-) If the short field takoff is using a higher drag, higher lift configuration (more flaps) to get off the ground at a lower speed (shorter roll) it then takes longer (in both time and distance) to make the climb over the obstacle because of the higher drag configuration. I hope this makes sense. Yes, it makes sense, but I don't think it always holds up in practice. For example, in my Mooney, the recommended obstacle clearance technique is to not retract the gear until the obstacle is cleared. More drag gives a greater -angle- of climb. In the Helio, the shortest ground roll is with 40 degrees of flaps but the shortest distance over a 50' obstacle is with 30 degrees of flaps. It seems the configuration for best angle is model-specific. |
#22
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"Dave Butler" wrote in message ... Mike Rapoport wrote: wrote in message ... Mike Rapoport wrote: : Keep in mind that the short field settings shorten the ground run but : generally increase the distance to clear a 50' obstical. Isn't that the *point* of short field technique... to get off and over in the shortest distance? There would appear to be a logical flaw to that statement. I would agree that it will take more *time* to get to a given altitude at (e.g. 50' obstacle clearance)... Short field performance is defined to give the best obstacle clearance per *distance*. I would agree that soft-field technique will increase distance, but short is short. Am I missing something? Maybe :-) If the short field takoff is using a higher drag, higher lift configuration (more flaps) to get off the ground at a lower speed (shorter roll) it then takes longer (in both time and distance) to make the climb over the obstacle because of the higher drag configuration. I hope this makes sense. Yes, it makes sense, but I don't think it always holds up in practice. For example, in my Mooney, the recommended obstacle clearance technique is to not retract the gear until the obstacle is cleared. More drag gives a greater -angle- of climb. In the Helio, the shortest ground roll is with 40 degrees of flaps but the shortest distance over a 50' obstacle is with 30 degrees of flaps. It seems the configuration for best angle is model-specific. More drag, by itself, can't improve angle of climb. They must have had another reason. Mike MU-2 |
#23
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In article , xyzzy wrote:
BTIZ wrote: I fly a warrior. If I am not doing a short field technique I usually take off with one notch of flaps. In the Comanche one notch of flaps makes for a much crisper transition from rolling to flying. The takeoff angle is noticably steeper, too. -- Ben Jackson http://www.ben.com/ |
#24
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wrote in message ... Mike Rapoport wrote: : Maybe :-) If the short field takoff is using a higher drag, higher lift : configuration (more flaps) to get off the ground at a lower speed (shorter : roll) it then takes longer (in both time and distance) to make the climb : over the obstacle because of the higher drag configuration. I hope this : makes sense. : In the Helio, the shortest ground roll is with 40 degrees of flaps but the : shortest distance over a 50' obstacle is with 30 degrees of flaps. : Mike : MU-2 : Helio Courier OK... I'll buy that. My experience with performance charts is with a 172 and a PA-28. The latter is sorely lacking in much relevant detail. I would imagine much more precision and other ways to figure how to eek out the maximum poop from your Helio POH... that's what the plane's FOR! My PA-28 book makes no distinction. Just says, "Max effort, 25 degree flaps over 50'" It might not matter, but I don't info one way or the other. -Cory Actually the Helio manual is abysmal compared to the MU-2 manual which I attibute to the age of the Helio (1974) to the MU-2 (1982). The Helio manual does devote a lot of space to STOL techniques though. Manuals keep getting thinker and thicker as time goes on...the FAA and lawers love paper! Mike MU-2 |
#25
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Yes, it makes sense, but I don't think it always holds up in practice. For example, in my Mooney, the recommended obstacle clearance technique is to not retract the gear until the obstacle is cleared. More drag gives a greater -angle- of climb. I did some extensive testing in a Beech Sierra and discovered that gear up or down makes extremely little difference below Vy. Less than I could reliably notice. |
#26
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"Roy Page" wrote in message ink.net...
I have been trying to determine the length of a runway that would be considered a "short field" for my Archer II. Whether or not a field is short depends quite a bit on the density altitude. A 2800 ft. runway at sea level and 69F isn't a short field for the Archer. The same runway at 7,500 ft. and 100F is probably to short even for the short field procedure. Basically, the POH takeoff calculation for the particular runway will tell you how much runway you'll need for a particular runway/altitude/temperature combination. Do the calculation, add a fudge factor, then decide whether or not the POH short field procedure should be used. John Galban=====N4BQ (PA28-180) |
#27
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"Mike Rapoport" wrote in message nk.net... "Dave Butler" wrote in message ... Mike Rapoport wrote: wrote in message ... Mike Rapoport wrote: : Keep in mind that the short field settings shorten the ground run but : generally increase the distance to clear a 50' obstical. Isn't that the *point* of short field technique... to get off and over in the shortest distance? There would appear to be a logical flaw to that statement. I would agree that it will take more *time* to get to a given altitude at (e.g. 50' obstacle clearance)... Short field performance is defined to give the best obstacle clearance per *distance*. I would agree that soft-field technique will increase distance, but short is short. Am I missing something? Maybe :-) If the short field takoff is using a higher drag, higher lift configuration (more flaps) to get off the ground at a lower speed (shorter roll) it then takes longer (in both time and distance) to make the climb over the obstacle because of the higher drag configuration. I hope this makes sense. Yes, it makes sense, but I don't think it always holds up in practice. For example, in my Mooney, the recommended obstacle clearance technique is to not retract the gear until the obstacle is cleared. More drag gives a greater -angle- of climb. In the Helio, the shortest ground roll is with 40 degrees of flaps but the shortest distance over a 50' obstacle is with 30 degrees of flaps. It seems the configuration for best angle is model-specific. More drag, by itself, can't improve angle of climb. They must have had another reason. I agree. Our C210 POH specifies the same (retract gear AFTER obstacle clearance), and my understanding is that it's because the transition to gear up involves the opening of the doors, etc, which causes a momentary INCREASE in drag. Cheers, John Clonts Temple, Texas N7NZ |
#29
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Well Mike, I do not have a PA-28-181 POH handy so I checked my old PA-32-300
At sea level, At Max GW Normal take off, 10degree flap setting, Ground Roll, 1050ft, 50ft clearance 1500ft Short Field take off, 25degree flap setting, Ground Roll, 950ft, 50ft clearance, 1400ft. Say again? BT "Mike Rapoport" wrote in message ink.net... The problem with this logic is that the 50' obstical distance is genarally greater with the short field flap setting. Only the ground run is shorter. Mike MU-2 |
#30
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"BTIZ" wrote in message news:%tcnd.106330$bk1.58516@fed1read05... Well Mike, I do not have a PA-28-181 POH handy so I checked my old PA-32-300 At sea level, At Max GW Normal take off, 10degree flap setting, Ground Roll, 1050ft, 50ft clearance 1500ft Short Field take off, 25degree flap setting, Ground Roll, 950ft, 50ft clearance, 1400ft. Say again? BT "Mike Rapoport" wrote in message ink.net... The problem with this logic is that the 50' obstical distance is genarally greater with the short field flap setting. Only the ground run is shorter. Mike MU-2 I won't argue with your POH! Does it give the speeds on both takeoffs? Mike MU-2 |
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