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Flight report & question-701

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lgold(at)quantum-associat
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Posted: Wed Jan 16, 2008 12:38 pm Post subject: Flight report & question-701

<?xml:namespace prefix = o ns =  "urn:schemas-microsoft-com:office:office" /> After 7 air-hours in my CH  701, I can report how it flies and need to  ask a question. 

The  flying. 

I don’t have all the  information yet, but here is what I can tell  you:

- Empty weight 650# with the CG 373 mm behind slats

- Develops  Max level-flight RPM of 5400 w/ 3 blade Warpdrive set 12°

-  Stall (at 2000-RPM idle) slightly under 30-MPH (GPS)

- Best  glide angle is about 60-MPH at 2000-RPM idle

- Flies about 85-MPH at 4900-RPM  

  (I will add streamlined strut  covers and hope to cruise 90-MPH)

- Best  climb at 55-MPH (about  1200’/m w/20 Gal fuel & 180’  pilot)

- Tracks well. Holds altitude hands off between 40 & 85 MPH (w/ el. trim) 

- EZ autopilot and  Dynon 180 work great and are recommended  

The  question. 

Is it normal for the  701 to try to reach a very high angle-of-attack at lift off? The stick on my 701  pulls itself firmly back and I have to push it forward to prevent the 701 from  going into very high angle of attack, slowing the plane to near stall speed. It  probably wouldn’t stall, but I don’t want to be in this configuration in case of  an engine stoppage. Note that the elevator trim tab is in neutral position  during take-off and the plane trims out very well using the trim tab in all but  very high RPM conditions. 

If this is not a  normal 701 characteristic, I can think of two factors that may be causing it,  and can use advice from those of you who have also experienced this  condition.    The first factor I can do little    about. Because I added about 40# of BRS chute and reinforcing structure behind    the baggage compartment, my 701 is a little tail heavy, but well within the    allowed GC range (e.g., when I was flying yesterday with 20 gal fuel, my CG    was about 450mm behind the slats. Zenith says you’re OK from 280 to 500mm).       
The second factor I can probably deal    with. When I was installing the controls I noticed that the stick sprang back    from the far right when pushed side-to side to test the aileron control. It    took a while to discover that this was caused by tight elevator cables. After    first few flights (with a passenger aboard where the take-off effect was not    as great) I loosened the upper cable about ¼” at the turnbuckle near the    forward bellcrank (this is the cable attached to bottom of the elevator &    pulls the el. down). The elevator cable can now swing an inch or two in the    middle when the bungees are not attached to them, but the stick no longer    springs back. Could loosing this cable be causing the problem? If so I    apparently have a choice of having a spring-back (which probably means the el.    control cable is too tight), or a potential take-off attitude    problem. 

I guess I could just  set the trim tab to lower the nose at take off. Is this what you experienced  701’ers do? 

Thanks for the advice,  

Les

 

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bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Wed Jan 16, 2008 1:15 pm Post subject: Flight report & question-701

No, this is not normal behavior for any aircraft. The airplane trim 

should be set before take off so that the airplane tends to hold climb 

attitude on it's own after takeoff. If this requires an excessive amount 

of trim tab deflection to achieve, you may have to change the angle of 

incidence of the horizontal stabilizer to correct this. It sounds like 

the leading edge of your stabilizer needs to be raised a bit since you 

are running out of trim at high RPM. At cruise airspeed, the trim tab 

should be somewhere near the neutral position.



I had the opposite problem with my 601. I didn't have enough nose down 

trim available. I made new attachment brackets for the front of my 

horizontal stabilizer in order to lower the leading edge about 3/8th of 

an inch.



Les Goldner wrote:

 	  Quote: 	
		   

 Is it normal for the 701 to try to reach a very high angle-of-attack at 

 lift off? The stick on my 701 pulls itself firmly back and I have to 

 push it forward to prevent the 701 from going into very high angle of 

 attack, slowing the plane to near stall speed. It probably wouldn’t 

 stall, but I don’t want to be in this configuration in case of an engine 

 stoppage. Note that the elevator trim tab is in neutral position during 

 take-off and the plane trims out very well using the trim tab in all but 

 very high RPM conditions.

 

 

 I guess I could just set the trim tab to lower the nose at take off. Is 

 this what you experienced 701’ers do?

 

 Thanks for the advice,

 Les

  

-- 
	


Bryan Martin

Zenith 601XL N61BM

Ram Subaru, Stratus redrive

Do Not Archive

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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

NYTerminat(at)aol.com
Guest

Posted: Wed Jan 16, 2008 4:04 pm Post subject: Flight report & question-701

Les, I offer the following advise for  your 701.

  

  In a message dated 1/16/2008 3:39:58 P.M. Eastern Standard Time,  lgold(at)quantum-associates.com writes:

  	  Quote: 	
		     

After 7 air-hours in my CH 701, I can report how it flies and need to ask a    question.   

The    flying.   

I donâ€™t have all the    information yet, but here is what I can    tell you:

- Empty weight 650# with the CG 373 mm behind slats

-    Develops Max level-flight RPM of 5400 w/ 3 blade Warpdrive set    12Â° You should be getting near 5800 RPM on your wide open    RPM in flight, reduce your pitch a little    bit.

- Stall (at    2000-RPM idle) slightly under    30-MPH (GPS)

- Best glide angle is about 60-MPH at 2000-RPM idle

- Flies    about 85-MPH at 4900-RPM 

  (I    will add streamlined strut covers and hope to cruise 90-MPH)You will.

- Best climb at 55-MPH (about 1200â€™/m    w/20 Gal fuel & 180â€™ pilot)

- Tracks well. Holds altitude hands    off between 40 & 85 MPH (w/ el.    trim) 

- EZ autopilot and Dynon 180 work great and are recommended       

The    question.   

Is it normal for the    701 to try to reach a very high angle-of-attack at lift off? The stick on my    701 pulls itself firmly back and I have to push it forward to prevent the 701    from going into very high angle of attack, slowing the plane to near stall    speed.This does not happen with mine, you need to    apply some back pressure to rotate and climb  It    probably wouldnâ€™t stall, but I donâ€™t want to be in this configuration in case    of an engine stoppage. Note that the elevator trim tab is in neutral position    during take-off and the plane trims out very well using the trim tab in all    but very high RPM conditions. When in cruise what    position is your elevator trim in? Is it in the neutral position or do you    have to use trim to pitch the nose    down?     

If this is not a    normal 701 characteristic, I can think of two factors that may be causing it,    and can use advice from those of you who have also experienced this    condition.        The first factor I can do little      about. Because I added about 40# of BRS chute and reinforcing structure      behind the baggage compartment, my 701 is a little tail heavy, but well      within the allowed GC range (e.g., when I was flying yesterday with 20 gal      fuel, my CG was about 450mm behind the slats. Zenith says youâ€™re OK from 280      to 500mm). Where is your battery      installed?      
The second factor I can probably      deal with. When I was installing the controls I noticed that the stick      sprang back from the far right when pushed side-to side to test the aileron      control. It took a while to discover that this was caused by tight elevator      cables. After first few flights (with a passenger aboard where the take-off      effect was not as great) I loosened the upper cable about Â¼â€ at the      turnbuckle near the forward bellcrank (this is the cable attached to bottom      of the elevator & pulls the el. down).This      should not do it but you should recheck your elevator travel up and down for      the correct degrees of travel The elevator cable can      now swing an inch or two in the middle when the bungees are not attached to      them, but the stick no longer springs back. Could loosing this cable be      causing the problem? If so I apparently have a choice of having a      spring-back (which probably means the el. control cable is too tight), or a      potential take-off attitude problem.   

I guess I could just    set the trim tab to lower the nose at take off. Is this what you experienced    701â€™ers do? I use full up trim for take off, in    cruise the trim is centered. Bob Spudis    N701ZX/912S/140hrs   

Thanks for the    advice, 

Les

 	




Start the year off right.  Easy ways to stay in shape in the new year. 

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jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Thu Jan 17, 2008 1:11 am Post subject: Re: Flight report & question-701

Les,

   Bob has said mostly what I was about to say- I will just add some notes about my 701 characteristics



I usually T/O with full up trim set and flap (16 deg). this is a rev-4 1100lbs

with Jabiru 2200a engine.



My first takeoffs did feel as if the aircraft was over-rotating with a pitch up on liftoff. I have become accustomed to this characteristic, as if the centre of lift pressure under the wing is moving forward when the AofA is increased. The stick has never pushed itself aft or required any down pressure my me to correct, as far as I remember. Perhaps the effect is worse with zero flap. Perhaps you have more power making the elevator authority even more sensitive to power settings - which it is designed to be. Dont worry about the pitch if the engine stops - if your cg is correct the nose will come down in heaps because propwash is gone from the elevator.



My empty wt is 590 lbs and cg 310mm (21%MAC) and this situation works out  that with full fuel and crew to 1100 lbs I require zero load in aft baggage area to be within the aft cg limit. My battery and as much stuff as practical is stowed forward as possible.



The elevator cables  / aileron tensioning I have learnt to live with. but plan to experiment with a bungee to hold the aileron over to the right so the stick sits in the middle instead of being propped up by my leg most of the time. It might have been nicer to have it tensioning on left aileron, as its easier to fly with the weight of your arm pulling towards you than pushing away. I think to change this would need a reversal of most of the elevator horn setup. If the cables are too loose, the elevator tends to bump a bit taxying in tailwinds.



I have written to ZAC about how to tension the cables and asking what the revised flap limit speed is for the 16 deg max. flaps and why, but have not found any answer. My build instructions have no details of these things.



Regards, Ralph

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Ralph - CH701 / 2200a

dkandle

Joined: 23 Apr 2007
Posts: 10
Location: Boise ID

Posted: Tue Jan 29, 2008 12:11 pm Post subject: Re: Flight report & question-701

I have about 90 hours on my 701 and I discovered a few weeks ago that with full back elevator, and full (or nearly so) power you can put the tail into the dirt.

I was landing on a dirt strip and hit a mud puddle.  I went to add power to keep from getting bogged down but added a bit too much power.  I rotated the tail right into the ground.

My plane is very stock.  With no one in the plane, if you push the tail all the way down it will stay put with the tail on the ground (don't remember how much fuel I had when I tried this).  So, when the weight of the plane is on the wheels (as opposed to the wings), once the tail gets to a certain point it doesn't take too much more down force to take it all the way down.  Clearly the prop blast provides enough elevator authority to push the tail to the ground.

On the 701 I start my ground roll with neutral elevator and when the airspeed moves past 20 I gently lift the nose.  On my Cessna 206 I start with the control all the way aft and relax pressure as the nose lifts.  If I were to start the takeoff in the 701 with the control all the way back I could easily see how it would simply take the tail all the way down as it all happens so fast.

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lgold(at)quantum-associat
Guest

Posted: Tue Jan 29, 2008 7:14 pm Post subject: Flight report & question-701

My 701 tail also stays down if you push it to the ground and also tries to

climb very steeply on takeoff if I don't set the trim down. I attribute this

to the 40# of BRS chute behind the baggage compartment, which puts my empty

CG toward the back of the allowed range (about 375mm aft of the front of the

slats). 



The CG in my 701 / Rotax 912ULS is, however, within the allowed range (just

under than 500mm aft limit) even with 370# pilot-passenger, 20 Gal. of fuel,

and 50# of baggage. 



Can you tell us what engine you have, where does your empty CG fall, and

what is the weight of your 701? (You could also have an aft GC if your

engine is lighter than my 912, even without a chute). With a lighter engine

your AOA could go very high.



Did you do much damage to your plane when the tail hit?



Regards,

Les 

 



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dkandle

Joined: 23 Apr 2007
Posts: 10
Location: Boise ID

Posted: Sat Feb 02, 2008 8:17 pm Post subject: Re: Flight report & question-701

 	  Quote: 	
		  My 701 tail also stays down if you push it to the ground and also tries to

climb very steeply on takeoff if I don't set the trim down. ...



Can you tell us what engine you have, where does your empty CG fall, and

what is the weight of your 701?  ...

Did you do much damage to your plane when the tail hit?



Regards,

Les 

 



	




Les:  I have a 912ULS and use a rather light Osprey battery located behind the seat (normal location).  I don't have my paperwork in front of me, but my empty weight is about 590 lbs.



No real damage was done.  Just some scuff marks and a slightly bent rudder horn.  I think I'll put a skid on the back.  It also touched the rear lower part of the rudder.  This is one problem I see with this geometry.  The first part to hit is the rudder, not the rear tie-down ring.  My guess is that at some point they redesigned something (like the gear) and didn't make the corresponding change to the lower rudder line.

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lgold(at)quantum-associat
Guest

Posted: Sat Feb 02, 2008 10:49 pm Post subject: Flight report & question-701

dkendle,

FYI, I put a 4 or 5" thin skateboard wheel on a thick "L" angle at the back

bottom of the fus and also put a tie-down point there. I hope this will keep

the rudder off the runway.

Les



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