Considering Dropping Parachute Option
Posted: Thu Jul 29, 2021 8:57 am
Ive been running wt/cg numbers with realistic loading scenarios for my planned mission. 4 average wt people with a reasonable amount of bags. As you all know, keeping the landing cg from going out the back of the envelope is the challenge. Unless I'm doing something wrong with the numbers, the ability to add forward ballast as far forward as possible is a must.
I will be starting with Midwest Skysports and their build assist program as soon as my kit arrives. Henry Rise, the owner, suggested the best way to add forward wt would be to use the hollow interior of the nose strut. He gave me the interior detentions of 2 " in diameter and 25" of useable length. That yields 78.54 in3. If that space were completely filled with water it would only yield 2.83 lb. antifreeze would be only slightly heavier. Filling it with lead would be 32.2 lb. I'm not sure how easy the access is going to be from the top but the ability to add and remove small bags of lead shot would be nice. The ability to add wt to the nose tire itself by filling it with polyurethane foam may also be an option.
The POH shows the nose wheel at 18.268 in aft of Datum. I used 20 in for the added ballast since the strut angles aft slightly as you go up. The more wt you add the greater that number would be since the top of the tube is farther aft than the bottom.
My realistic loading scenario is :
Seats - LF 170 lb, RF 190, LR 115, RR 122
Bags - 59 lb
Landing Fuel - 9 gal
My sample aircraft are - N678CB without parachute. Empty wt 1156, Empty cg 19.69, Empty moment 85081.6
- N135WT with parachute. 1184, 23.57, 89573.6
IF my math is correct, in order to bring the landing cg back into limits, 16.11 lb of forward ballast would be required without parachute and 52.13 lb with parachute. I could live with putting 16 lb or so up there and just leaving it but a total parachute penalty of over 100 lb is enough to drop the parachute option. Im hoping my math is off somewhere.
side note: I was fortunate enough to travel to the factory in SA just before covid came along and get an extensive factory tour. My wife and I flew with James Pitman for over an hour, super guy with lots of energy. We talked a good bit about the parachute and he strongly recommended against it. He said the aircraft is designed to not have it but they included the option later for those who insisted on it. He said it really screws up the CG....now I get it!
I will be starting with Midwest Skysports and their build assist program as soon as my kit arrives. Henry Rise, the owner, suggested the best way to add forward wt would be to use the hollow interior of the nose strut. He gave me the interior detentions of 2 " in diameter and 25" of useable length. That yields 78.54 in3. If that space were completely filled with water it would only yield 2.83 lb. antifreeze would be only slightly heavier. Filling it with lead would be 32.2 lb. I'm not sure how easy the access is going to be from the top but the ability to add and remove small bags of lead shot would be nice. The ability to add wt to the nose tire itself by filling it with polyurethane foam may also be an option.
The POH shows the nose wheel at 18.268 in aft of Datum. I used 20 in for the added ballast since the strut angles aft slightly as you go up. The more wt you add the greater that number would be since the top of the tube is farther aft than the bottom.
My realistic loading scenario is :
Seats - LF 170 lb, RF 190, LR 115, RR 122
Bags - 59 lb
Landing Fuel - 9 gal
My sample aircraft are - N678CB without parachute. Empty wt 1156, Empty cg 19.69, Empty moment 85081.6
- N135WT with parachute. 1184, 23.57, 89573.6
IF my math is correct, in order to bring the landing cg back into limits, 16.11 lb of forward ballast would be required without parachute and 52.13 lb with parachute. I could live with putting 16 lb or so up there and just leaving it but a total parachute penalty of over 100 lb is enough to drop the parachute option. Im hoping my math is off somewhere.
side note: I was fortunate enough to travel to the factory in SA just before covid came along and get an extensive factory tour. My wife and I flew with James Pitman for over an hour, super guy with lots of energy. We talked a good bit about the parachute and he strongly recommended against it. He said the aircraft is designed to not have it but they included the option later for those who insisted on it. He said it really screws up the CG....now I get it!