---------------------------------------------------------- Zenith-List Digest Archive --- Total Messages Posted Sun 11/02/03: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:13 AM - 601 exhaust movement (Richard McLachlan) 2. 07:52 AM - Re: Crash 701- another one (Carl Bertrand) 3. 09:06 AM - Re: N701XL Flies! (JERICKSON03E@aol.com) 4. 09:09 AM - Re: Crash 701- another one (Dirk Slabbert) 5. 09:26 AM - Re: Crash 701- another one (Steve Dixon) 6. 12:03 PM - Re: N701XL Flies! (Dabusmith@aol.com) 7. 06:07 PM - New 5th Edition HD/HDS Drawings! (Doug Waer) ________________________________ Message 1 _____________________________________ Time: 01:13:31 AM PST US From: Richard McLachlan Subject: Zenith-List: 601 exhaust movement We have a 601HDS with the Rotax 912 engine. When we bought the a/c the original builder had fitted his own stainless steel exhaust system, which had no baffles in the silencer (muffler). Due to noise complaints, we replaced this with the original Zenith exhaust with the dual spring retained couplings. Problem is that with use one of the exhaust pipes gradually vibrates its way toward the cowling until it starts hitting against it. We already have the securing bolt as tight as we dare go without stripping the thread. --> Zenith-List message posted by: Richard McLachlan Does anybody know any reason why we should not fit a pair of SS securing straps from each silencer body to a central point under the engine? This would prevent the movement but may also prevent the spring couplings moving. -- Richard McLachlan CH601HDS/R22 Helicopter Landing Site info at http://www.rodsley.net ________________________________ Message 2 _____________________________________ Time: 07:52:30 AM PST US From: "Carl Bertrand" Subject: Re: Zenith-List: Crash 701- another one --> Zenith-List message posted by: "Carl Bertrand" Hi Rick, I was sorry to read about your accident. I hope you recover fully from your injuries and will again take to the air chalking the event to experience. I took particular interest in your accident because I also fly a 701. I scratch built in 94/95 and have over three hundred hours mostly on floats; half with the ZAC wings and half with my own design auto slat wings (very similar to the dedalius design). In my case I find handling to be very similar with both designs and in my opinion the differences were not a factor in your accident. Before I committed to building my new wing I did a long series of test on a 6' full scale section with slat and flap. With tufts in place, I video recorded air flow at all angles of attack from 0 to 30 and with the flaps at 0,15, 30 degrees. I conducted these test with the slat "in", "out", and "free" at speeds up to 50 mph. For me the results were very informative and gave me the confidence I needed to proceed with building and flight testing the wings. I must state that although I have not flown the dedalius wings, I can state with assurance that the flight characteristics of the ZAC and my design are much the same and suspect that the dedalius wing is also similar. The wing design in the 701 with slats and displaced flaps is optimized to develop very high lift at slow speed. The effect of the slots at the slats and the flaps results in stall angles in the 30 degree range as opposed to the more conventional wing at 17 degrees. Also, the elevator is optimized to be very effective for its size. This makes the a/c very manoeuvrable at low speed but like all a/c it has its limits. From your description of the accident, you only rolled "three to four meters" when the a/c rotated rapidly, became airborne, continued rotation to a steep angle, "tea bag", and then "went into a descent to the left from about 70 feet". In my opinion, I believe the a/c responded to the very strong control forces applied; mainly from the stab/elevator . With full power, the air flow over the full "UP" elevator caused the a/c to rotate early and rapidly changing the angle angle of attack from around 8 to somewhere greater than 25 degrees. As others have pointed out you became airborne prematurely because of ground effect but also the high lift wing design. Things would develop very quickly from that point for a number of reasons. At the approach of the critical angle we all know that lift quickly changes to drag. With this wing a lot of lift changes into a lot of drag. From my experiments, I found that the last areas to stall are behind the slots (Behind the slat to the main spar, and the flap). The flap continues to produce lift even when down 30 degrees and wing angle of attack is 28 degrees. However, once you're in that position you no longer have a high lift wing; you have a very effective speed brake. If you picture the a/c in that 30 degree position from the side, the drag vector from the wing is high and towards the front trying to rotate the a/c further. If you still had "UP"or even neutral elevator it accentuated the pitch-up because of its effecient inverted airfoil design. In addition, the rapid rotation at the start created momentum adding to the tendency to over rotate. Some of the forces that would help countered the rotation were: The lost of lift from the stalled wing; flying out of ground effect once above 15 to 20'; C of G; and ,any "down" elevator you applied. Once you rapidly passed through the 20 to 25 degree angle of attack, I don' believe the outcome could be changed much by any control inputs and only engine thrust could cushion the return to mother earth. In my experience 200 to 300 hundred feet would be needed to recover. After much experimentation, I've found that the following gives me the best short take-off performance. Take-off flaps, (25 degrees in my case) controls neutral, max RPM against the brakes, release brakes and accelerate to 20-25 mph then fairly smart back elevator until the nose starts to rise. Be prepared to rapidly check forward to stop rotation at 20-25 degrees.Once off the ground the a/c accelerates fairly quickly and you must feed in forward elevator to maintain the angle from increasing into a stall. At that stage I normally let the speed increase and reduce flaps to 10 degrees before climbing out of ground effect. If end of runway obstacle are a problem I keep flaps at 20 until clear. My only excuse for this long reply is that writing is not my strong suit. Best wishes for the rebuild. Carl ----- Original Message ----- From: "Rick Morawski" Subject: Re: Zenith-List: Crash 701- another one > --> Zenith-List message posted by: "Rick Morawski" > ________________________________ Message 3 _____________________________________ Time: 09:06:15 AM PST US From: JERICKSON03E@aol.com Subject: Re: Zenith-List: N701XL Flies! --> Zenith-List message posted by: JERICKSON03E@aol.com Dave, Great job. Fly safely & enjoy. Jerry Erickson 701SP in work ________________________________ Message 4 _____________________________________ Time: 09:09:43 AM PST US From: "Dirk Slabbert" Subject: Re: Zenith-List: Crash 701- another one --> Zenith-List message posted by: "Dirk Slabbert" Carl, your post is really an eye opener, shakes out all the cobwebs! Thanks, it will probably keep me out of harms way, or my bones from the lions mouth.......he hee hee.. Dirk (bush pilot in Africa) ----- Original Message ----- From: Carl Bertrand To: zenith-list@matronics.com Sent: Sunday, November 02, 2003 5:53 PM Subject: Re: Zenith-List: Crash 701- another one --> Zenith-List message posted by: "Carl Bertrand" Hi Rick, I was sorry to read about your accident. I hope you recover fully from your injuries and will again take to the air chalking the event to experience. I took particular interest in your accident because I also fly a 701. I scratch built in 94/95 and have over three hundred hours mostly on floats; half with the ZAC wings and half with my own design auto slat wings (very similar to the dedalius design). In my case I find handling to be very similar with both designs and in my opinion the differences were not a factor in your accident. Before I committed to building my new wing I did a long series of test on a 6' full scale section with slat and flap. With tufts in place, I video recorded air flow at all angles of attack from 0 to 30 and with the flaps at 0,15, 30 degrees. I conducted these test with the slat "in", "out", and "free" at speeds up to 50 mph. For me the results were very informative and gave me the confidence I needed to proceed with building and flight testing the wings. I must state that although I have not flown the dedalius wings, I can state with assurance that the flight characteristics of the ZAC and my design are much the same and suspect that the dedalius wing is also similar. The wing design in the 701 with slats and displaced flaps is optimized to develop very high lift at slow speed. The effect of the slots at the slats and the flaps results in stall angles in the 30 degree range as opposed to the more conventional wing at 17 degrees. Also, the elevator is optimized to be very effective for its size. This makes the a/c very manoeuvrable at low speed but like all a/c it has its limits. From your description of the accident, you only rolled "three to four meters" when the a/c rotated rapidly, became airborne, continued rotation to a steep angle, "tea bag", and then "went into a descent to the left from about 70 feet". In my opinion, I believe the a/c responded to the very strong control forces applied; mainly from the stab/elevator . With full power, the air flow over the full "UP" elevator caused the a/c to rotate early and rapidly changing the angle angle of attack from around 8 to somewhere greater than 25 degrees. As others have pointed out you became airborne prematurely because of ground effect but also the high lift wing design. Things would develop very quickly from that point for a number of reasons. At the approach of the critical angle we all know that lift quickly changes to drag. With this wing a lot of lift changes into a lot of drag. From my experiments, I found that the last areas to stall are behind the slots (Behind the slat to the main spar, and the flap). The flap continues to produce lift even when down 30 degrees and wing angle of attack is 28 degrees. However, once you're in that position you no longer have a high lift wing; you have a very effective speed brake. If you picture the a/c in that 30 degree position from the side, the drag vector from the wing is high and towards the front trying to rotate the a/c further. If you still had "UP"or even neutral elevator it accentuated the pitch-up because of its effecient inverted airfoil design. In addition, the rapid rotation at the start created momentum adding to the tendency to over rotate. Some of the forces that would help countered the rotation were: The lost of lift from the stalled wing; flying out of ground effect once above 15 to 20'; C of G; and ,any "down" elevator you applied. Once you rapidly passed through the 20 to 25 degree angle of attack, I don' believe the outcome could be changed much by any control inputs and only engine thrust could cushion the return to mother earth. In my experience 200 to 300 hundred feet would be needed to recover. After much experimentation, I've found that the following gives me the best short take-off performance. Take-off flaps, (25 degrees in my case) controls neutral, max RPM against the brakes, release brakes and accelerate to 20-25 mph then fairly smart back elevator until the nose starts to rise. Be prepared to rapidly check forward to stop rotation at 20-25 degrees.Once off the ground the a/c accelerates fairly quickly and you must feed in forward elevator to maintain the angle from increasing into a stall. At that stage I normally let the speed increase and reduce flaps to 10 degrees before climbing out of ground effect. If end of runway obstacle are a problem I keep flaps at 20 until clear. My only excuse for this long reply is that writing is not my strong suit. Best wishes for the rebuild. Carl ----- Original Message ----- From: "Rick Morawski" To: Subject: Re: Zenith-List: Crash 701- another one > --> Zenith-List message posted by: "Rick Morawski" > ________________________________ Message 5 _____________________________________ Time: 09:26:04 AM PST US From: "Steve Dixon" Subject: Re: Zenith-List: Crash 701- another one --> Zenith-List message posted by: "Steve Dixon" Carl, I think you should reassess your last statement, that was (IMHO) beautifully done and VERY informative. I have printed it to use when my 701 is done and flying. THANKS!! Steve Dixon DO NOT ARCHIVE ----- Original Message ----- From: "Carl Bertrand" Subject: Re: Zenith-List: Crash 701- another one > --> Zenith-List message posted by: "Carl Bertrand" > > Hi Rick, > I was sorry to read about your accident. I hope you recover fully from your > injuries and will again take to the air chalking the event to experience. > I took particular interest in your accident because I also fly a 701. I > scratch built in 94/95 and have over three hundred hours mostly on floats; > half with the ZAC wings and half with my own design auto slat wings (very > similar to the dedalius design). In my case I find handling to be very > similar with both designs and in my opinion the differences were not a > factor in your accident. > Before I committed to building my new wing I did a long series of test on a > 6' full scale section with slat and flap. With tufts in place, I video > recorded air flow at all angles of attack from 0 to 30 and with the flaps at > 0,15, 30 degrees. I conducted these test with the slat "in", "out", and > "free" at speeds up to 50 mph. For me the results were very informative and > gave me the confidence I needed to proceed with building and flight testing > the wings. I must state that although I have not flown the dedalius wings, I > can state with assurance that the flight characteristics of the ZAC and my > design are much the same and suspect that the dedalius wing is also similar. > The wing design in the 701 with slats and displaced flaps is optimized to > develop very high lift at slow speed. The effect of the slots at the slats > and the flaps results in stall angles in the 30 degree range as opposed to > the more conventional wing at 17 degrees. Also, the elevator is optimized to > be very effective for its size. This makes the a/c very manoeuvrable at low > speed but like all a/c it has its limits. > From your description of the accident, you only rolled "three to four > meters" when the a/c rotated rapidly, became airborne, continued rotation to > a steep angle, "tea bag", and then "went into a descent to the left from > about 70 feet". In my opinion, I believe the a/c responded to the very > strong control forces applied; mainly from the stab/elevator . With full > power, the air flow over the full "UP" elevator caused the a/c to rotate > early and rapidly changing the angle angle of attack from around 8 to > somewhere greater than 25 degrees. As others have pointed out you became > airborne prematurely because of ground effect but also the high lift wing > design. > Things would develop very quickly from that point for a number of reasons. > At the approach of the critical angle we all know that lift quickly changes > to drag. With this wing a lot of lift changes into a lot of drag. From my > experiments, I found that the last areas to stall are behind the slots > (Behind the slat to the main spar, and the flap). The flap continues to > produce lift even when down 30 degrees and wing angle of attack is 28 > degrees. However, once you're in that position you no longer have a high > lift wing; you have a very effective speed brake. > If you picture the a/c in that 30 degree position from the side, the drag > vector from the wing is high and towards the front trying to rotate the a/c > further. If you still had "UP"or even neutral elevator it accentuated the > pitch-up because of its effecient inverted airfoil design. In addition, the > rapid rotation at the start created momentum adding to the tendency to over > rotate. Some of the forces that would help countered the rotation were: The > lost of lift from the stalled wing; flying out of ground effect once above > 15 to 20'; C of G; and ,any "down" elevator you applied. Once you rapidly > passed through the 20 to 25 degree angle of attack, I don' believe the > outcome could be changed much by any control inputs and only engine thrust > could cushion the return to mother earth. In my experience 200 to 300 > hundred feet would be needed to recover. > After much experimentation, I've found that the following gives me the best > short take-off performance. Take-off flaps, (25 degrees in my case) > controls neutral, max RPM against the brakes, release brakes and accelerate > to 20-25 mph then fairly smart back elevator until the nose starts to rise. > Be prepared to rapidly check forward to stop rotation at 20-25 degrees.Once > off the ground the a/c accelerates fairly quickly and you must feed in > forward elevator to maintain the angle from increasing into a stall. At that > stage I normally let the speed increase and reduce flaps to 10 degrees > before climbing out of ground effect. If end of runway obstacle are a > problem I keep flaps at 20 until clear. > My only excuse for this long reply is that writing is not my strong suit. > Best wishes for the rebuild. > Carl > > > ----- Original Message ----- > From: "Rick Morawski" > To: > Subject: Re: Zenith-List: Crash 701- another one > > > > --> Zenith-List message posted by: "Rick Morawski" > > > > > ________________________________ Message 6 _____________________________________ Time: 12:03:30 PM PST US From: Dabusmith@aol.com Subject: Re: Zenith-List: N701XL Flies! --> Zenith-List message posted by: Dabusmith@aol.com Jerry Thanks for the kind words! This plane is great fun. It is snowing here today so I haven't been able to fly it. Get building! Dave ________________________________ Message 7 _____________________________________ Time: 06:07:18 PM PST US From: Doug Waer Subject: Zenith-List: New 5th Edition HD/HDS Drawings! --> Zenith-List message posted by: Doug Waer Was poking aroung the Zenith site, and noticed that they JUST updated the HD/HDS drawings to a 5th edition last friday (10/31). This should put to rest the whole idea that Zenith was essentially end-of-life'ing the HD/HDS series in favor of the XL. The drawings can be updated for $50. Heck, I'd get an update if for no other reason that my drawings have taken quite a beating in the last year! Doug Waer 601HDS ===== Douglas Waer :: Boeing Helicopter Systems :: Mesa, AZ :: 85215 http://members.cox.net/dwaer/flying.html __________________________________