---------------------------------------------------------- Allegro-List Digest Archive --- Total Messages Posted Thu 07/31/08: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:05 AM - Re: Take-off Distance for Allegro 2000 (Thomas R. Riddle) 2. 05:34 AM - Re: Take-off Distance for Allegro 2000 (Hugh) 3. 09:11 AM - Re: Re: Wheel Bearing Inspection/Lubrication (Hugh) ________________________________ Message 1 _____________________________________ Time: 04:05:24 AM PST US From: "Thomas R. Riddle" Subject: Re: Allegro-List: Take-off Distance for Allegro 2000 Hugh, There are other variables that you did not mention that can have a dramatic effect on rate of climb and take-off distances. The most obvious is the pitch of the prop. Others, perhaps a little less obvious, include the condition of the engine and the technique and skill of the pilot. Also, which fuel are you burning? If it is E-10 it will be producing roughly 3 1/2% less power than if using auto fuel that is not laced with alcohol or 100LL. Also, the take-off distance varies greatly with type and condition of surface. I know a pilot in Hawaii who lives at ~4,000 msl with a short grass strip. He keeps one have the width mowed short for take-off and the other half mowed long for landing. That said, you can make an educated guess at rate of climb (ROC) at a given density altitude (DA) because it degrades at a nearly linear rate up to the service ceiling. Of course this requires knowledge of the service ceiling, which I would estimate to be around 15000' DA with the 80hp engine with the prop set for best cruise at low DA. I know I've had our Allegro up to 12500' msl and still getting about 400 fpm ROC. This was solo so at MTOW it would have been a good bit less ROC. I don't recall what the DA was at that altitude on that day but it was in cool weather. I think you are over analyzing this. The safest thing to do is do some take-off and climb testing at different weights and atmospheric conditions on a long runway with a helper to pace off the take-off roll. Since you live in North Carolina, you can fly to one of the highest elevation airports east of the Mississippi River in reasonable time and do the tests there too. There is nothing like empirical testing to get the information you want because that will be done with you at the flight controls and you controlling the loading etc. Get enough data points under enough varying conditions and you can extrapolate to get reasonably accurate figures under other conditions. This will likely be more useful than some theoretical numbers that do not take into account the variables not included in your original question. ________________________________ Message 2 _____________________________________ Time: 05:34:08 AM PST US From: "Hugh" Subject: RE: Allegro-List: Take-off Distance for Allegro 2000 Thom: Your points are well taken, but here is my situation. I have just filled my wing tanks for the first time and belly tank, and am at my home grass field N92 (i.e. max fuel load). The numbers you saw in my post are real. I have taken off from this field many times with a full belly tank and the same conditions as stated with a 200 lbs. passenger, 15 degrees on the prop, but no fuel in the wing tanks. Under those conditions I use about half of the 2000 foot grass runway. All conditions being the same, except for 65 more pounds of fuel in the wing, would my increase in take-off roll be linear or something else? Hugh -----Original Message----- From: owner-allegro-list-server@matronics.com [mailto:owner-allegro-list-server@matronics.com] On Behalf Of Thomas R. Riddle Sent: Thursday, July 31, 2008 7:03 AM Subject: Re: Allegro-List: Take-off Distance for Allegro 2000 Hugh, There are other variables that you did not mention that can have a dramatic effect on rate of climb and take-off distances. The most obvious is the pitch of the prop. Others, perhaps a little less obvious, include the condition of the engine and the technique and skill of the pilot. Also, which fuel are you burning? If it is E-10 it will be producing roughly 3 1/2% less power than if using auto fuel that is not laced with alcohol or 100LL. Also, the take-off distance varies greatly with type and condition of surface. I know a pilot in Hawaii who lives at ~4,000 msl with a short grass strip. He keeps one have the width mowed short for take-off and the other half mowed long for landing. That said, you can make an educated guess at rate of climb (ROC) at a given density altitude (DA) because it degrades at a nearly linear rate up to the service ceiling. Of course this requires knowledge of the service ceiling, which I would estimate to be around 15000' DA with the 80hp engine with the prop set for best cruise at low DA. I know I've had our Allegro up to 12500' msl and still getting about 400 fpm ROC. This was solo so at MTOW it would have been a good bit less ROC. I don't recall what the DA was at that altitude on that day but it was in cool weather. I think you are over analyzing this. The safest thing to do is do some take-off and climb testing at different weights and atmospheric conditions on a long runway with a helper to pace off the take-off roll. Since you live in North Carolina, you can fly to one of the highest elevation airports east of the Mississippi River in reasonable time and do the tests there too. There is nothing like empirical testing to get the information you want because that will be done with you at the flight controls and you controlling the loading etc. Get enough data points under enough varying conditions and you can extrapolate to get reasonably accurate figures under other conditions. This will likely be more useful than some theoretical numbers that do not take into account the variables not included in your original question. ________________________________ Message 3 _____________________________________ Time: 09:11:07 AM PST US From: "Hugh" Subject: RE: Allegro-List: Re: Wheel Bearing Inspection/Lubrication Roger: I have jacked the main gear wheels and checked the free rotation without load on the wheel. Both wheels turn freely for part of a revolution and then seem to drag on the brake pad and stop. I can feel the slight drag at one area when I slowly turn the wheel with my hand. My spare parts catalogue has a blank page where the main carriage with hydraulic brakes are listed, so I don't know if the main gear wheels have tapered or ball bearings. I visually checked the inside pad/disk clearance and can see no gap between the pad and the disk. This doesn't mean there is not a minute gap that can't be seen. The caliper unit does have some play in it which is normal, but should I be able to see a small gap between the inside pad and the disk, or not? I also notice that the visible ends of the two steel pins that retain the pads, (the ends that have cotter-pins in them) are protruding different lengths. The top steel pin protrudes more than the bottom steel pin. The outer pad is snug against the cotter-pin in the lower steel pin. Should these steel pins have free movement in them? The pads have plenty of material on them, so they appear to be fine. Any comments? The nose gear wheel rotates freely. Hugh -----Original Message----- From: owner-allegro-list-server@matronics.com [mailto:owner-allegro-list-server@matronics.com] On Behalf Of Roger Lee Sent: Wednesday, July 30, 2008 8:52 AM Subject: Allegro-List: Re: Wheel Bearing Inspection/Lubrication Hi Hugh, There are 1 or 2 little checks you should do. Jack one side up so the wheel is off the ground just a little and see if you can detect any wobble or odd noise from the wheel or the brakes. When wheels have some time on them the axial nut may need to be adjusted, usually a little tighter. See if the wheel turns freely or is it hanging up slightly or is there any movement from side to side. If you have standard straight ball bearing type wheel or tapered roller bearings. If you have the tapered roller bearing the wheel should only spin once around when you try to spin it. If it's the straight roller bearing type then it should spin freely several times. -------- Roger Lee Tucson, Az. 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