Jump to content

Rough Field Take Off


Runtoeat

Recommended Posts

Hi Runtoeat!

 

I'm referring to the nosegear, the mains are not my concern. I'm trying to keep the nosegear off the ground and as lightly loaded as much as possible. I haven't compared 15 to 35 degrees flaps settings, but I do know that at 35, I can almost lift the nose off without even starting the takeoff roll, and as I start down the runway, the nose gets so light I can lift it off before the dynon even registers an airspeed. I've watched my plane's shadow, and can see the nose strut extend some while pulling back all the way just after the start of the takeoff roll. Granted, this is on clean turf, it would mean less if you have to run the engine up slowly if you are rolling out on loose turf.

 

What's happening once the plane leaves the ground isn't what I was referring to :).

Link to comment
Share on other sites

If anyone has some graphics or a description of lift and drag at various flap settings, I'd like to have a reference to them.

 

Sometimes I got a little lost in the discussion of angle of attack versus pitch angle.

 

I fly out of one undulating grass strip and appreciate the interest in avoiding resettling after being air launched at a speed or condition that won't let one stay airborne.

Link to comment
Share on other sites

Something new to practice. It sounds like this technique would work for short, soft, or rough fields?

 

 

To be honest, you just have to try. Sandpiper's method would definitely be better on loose turf, where things could get picked up by the prop, so you have to slowly advance the throttle. I cannot answer the 35 vs 15 flaps at this time though, since I've never payed attention when using 15 on a soft field takeoff... I've only used that setting when there was wind.

 

I fly out of one undulating grass strip and appreciate the interest in avoiding resettling after being air launched at a speed or condition that won't let one stay airborne.

 

Columbus Southwest grass strip has a dip at the end of the runway opposite of the side with the house (this is an old airfield, and there's a HOUSE at the end of the field!). I've learned to just treat it like I was using a dirt bike when landing. I'll ride down into the depression, jump back into the air, and settle back on the runway. I could easily just overfly the depression, but that's one of the reasons I like to touch down there!

 

Anyways Jim, that's one of the things you just have to get a feel for!

Link to comment
Share on other sites

Anticept, thanks for the reply. My point IS what's happening while on the ground. Both front and main gear become light in a minimum time and distance with a full throttle, full flap takeoff. A CT taken off in this manner is like riding an elevator. You comment about your front gear immediately wanting to lift off the ground also applies to the mains with this procedure. Add a little headwind and the feeling is like you're in a express elevator. Also, you say "the mains are not my concern". I don't want this to be taken in the wrong way but I ask if you've been into a rough grass strip with a CTSW? If you have, you will appreciate my effort to lighten my main gear wheels as quickly as possible and be free from the field in a minimum time and distance. The aluminum struts on a CTSW are very stiff (increased in diameter to improve gear damage on hard landing after 2005 or so) and transmit a major amount of vibration into the airframe. I also fly a CTLS frequently and I really appreciate the composite main gear's ability to damp out the major portion of a rough grass field's input. Those who own CTLS's, do not take your composite gear for granted. This was a major upgrade done by FD!

 

Jim and Doug. My friend and I have tried this technique due to a launch from a rough and undulating ("woop-ded-doos") grass strip. On takeoff, a woopdee was encountered, the CT got launched in the air and came back down and struck the tail due to the nose high attitude from being held off the ground in the classical 15 flap rough field takeoff. With the full flap method, the thought is to hold the plane pretty much level with slight back pressure on initial roll to lighten the front gear and then to pply forward pressure to let it fly off on it's own and to not hold the nose off. We have demonstrated to ourselves using this method that a launch from a small rise under full flaps results in the plane settling back down in a slightly nose high but mainly level position because this is the attitude that was being targeted before the launch. After continuing on for a very short distance, the plane is in the air. Or if speed is nearing 40kts, the launch will put the plane in the air for good. Next, a flip to 15 flaps. I did not find that there was the major drop in altitude anticipated when this is done. Hold close to the ground and start the climb out when speed gets to 55kts. A word of caution here, as stated before. Full flaps produce major drag. If the Rotax engine stops while at minimum flying speed and under max drag with full flaps, our CT's will drop like a rock. One must remain close to the ground until the 15 flaps are initiated and required climb speed is achieved. Comments are always welcome.

Link to comment
Share on other sites

Hi Anticept. There will always be surprises when using unimproved strips. This method improves the chance for remaining damage free if/when a surprise is encountered. Thanks for your comments.

 

I would think 30 deg flap is your best setting for the technique your using. In my experience in the SW the CL max is a bit higher at 30 vs 40 based on the stall speeds being a couple knots slower at 30. Also there should be slightly less drag at 30 vs 40. You could also play with the manual flap setting capability in your SW and find a flap setting between 15 and 30 that is optimal for what your doing.

Link to comment
Share on other sites

A 30 flap take off works even if you are doing 30 flap touch and go's and screw it up you can go full throttle and switch flaps back in air. I have done a few 30 take offs, but make sure you have a little altitude and speed up off the runway because if you are too slow or low when going from 30 to 15 you can sink and tag the runway. I tend to be a little more level too instead of a lot of climb when I do the switch because it seems to give less sink and quicker speed increase.

Link to comment
Share on other sites

If you go back to the thread about my scary/botched landing with abort and look at the video, you'll see me lifting off with with 30° flaps. It left the ground flat and quick, I think at about 40 knots (I was too busy to get exact numbers...). Also I noticed that there was so much drag that the airplane didn't really want to go faster than 62kt (Vfe), even WOT, while climbing. Once I got a few hundred feet under me I went to 15° and accelerated to 75kt or so before going to 0°.

Link to comment
Share on other sites

I'm going to say again we need to see some wing numbers before we get too excited about a full or nearly full flap departure. We need to be especially careful about how this works at high altitude and gross weight. If what is being said is correct the physics will substantiate without me having to duplicate it on my own, so I'd like to see some numbers. Does anyone know where they can be found?

Stall speed is lower at 40° than 30° says FD and I've verified that in my own CTSW and in a friends CTSW.

Link to comment
Share on other sites

Just got back from flying today. My friend and I practiced all flaps settings for landing and take offs. Good practice with -6 ans 0 flap take off which established lift off from the runway about 72kts for -6 and about 67kts for 0. This gave us a visual for nose attitude at lift off. We came around and used the lift off speed for our landing speeds and held nose attitude similar as seen during take offs. Good practice for times when flaps might not be operational. Then, we repeated our high flap take offs. Eric points out 30 flaps are good for doing the rough field take offs. After flying today I agree because it does reduce the drag but still provides good AOA improvement. 30 flaps also requires only one click with the flap lever to get to 15 flaps after leaving the ground. Revisiting this process: Start with stick full back and apply power gradually to start the roll. Prop wash from extended flaps act on the elevator which immediately pushes the tail down and raises the nose off the ground. In 10 feet or less the nose is off and full power is now on. Now the stick is brought forward quickly and forward pressure is needed to keep plane level. In about 200 to 250 feet and 40kts, the plane is lifting off and all the while has been unloading the gear. Things happen quickly now. Speed builds very rapidly and as soon as you look away and back to the ASI, you will be at 50kts. Need to hold forward pressure on the stick to stay close to the ground while clicking to 15 flaps and be ready for a slight drop in altitude but no abrupt drop has been experienced by me. Speed continues to build quickly and 60kts is found just moments after going to 15 flaps and before expecting it. Start climb out to get over any obstacles. This is effective for getting off the ground in a minimum distance and at a level attitude and is fun. Give it a try.

Link to comment
Share on other sites

Haha Runtoeat, I just NOW got back from doing the tests myself at 35 and 15 degrees (on asphalt, testing on grass not yet completed because I need markers)! I was really pushing the limits for these tests, that was intense!

 

In addition to what you said, I did mine in a light crosswind. As a word of caution, be ready, because today I learned a crosswind with 35 degrees will pick up a wing before your aircraft is ready to fly, and you will start skipping on one wheel (I am calling the tendency for the airplane to kinda tip-toe and do little jumps on the runway skipping). So be aggressive with the aileron positioning for wind during takeoff!

 

Anyways, I repeated each test 2 times. With flaps at 35, I can get the nosewheel off the ground in just a few feet, and the aircraft is light on the wheels almost immediately (as said, skipped a little in that crosswind!). I repeated the test immediately with 15 degrees, and it did not want to skip. Repeated with 35, and again, the wheels wanted to skip before it was time to take off.

 

Also, you can climb with the nose below the horizon at 35. It's really freaking cool!

Link to comment
Share on other sites

Hi Anticept.....great that you tried it! Very important report on effect from x-wind when doing this method. Yes, the CT really does get light on it's feet in a very short distance taking off this way. This was the driver behind my friend coming up with this. Believe me, the less we owners of CTSW's spend running over rough ground with our landing gear taking a beating, the much better off we are. And, nose low attitude on grass fields means one will not have to try to lower it should there be engine problems at the first seconds of lift off or if the terrain launches the plane before it's ready to fly. The CT has some amazing capabilities. I just wish my abilities matched the capabilities. I guess whats fun about flying is there's always something we need to improve on. It is so fortunate that my experienced friend works with me to develop these sorts of things in a patient and safe way. Due to his professional manner and his flying experience, he can be depended on to not do something that would be unsafe but he does come up with some things I would not ever do if he weren't coaching me. The best thing is that I can pass on these things for others to try because of this forum.

Link to comment
Share on other sites

CT, you, sir, and our BC fliers and friends, are strangers in a strange land to a flat lander like me :blink: Too bad there's so many miles between me and the type of country you fly in which prevents me from experiencing it. I just can't imagine doing the type of flying you do.

Link to comment
Share on other sites

Glad you liked trying my way runtoeat :).

 

I figured there has to be a purpose for flap settings that high, and the back country flying i was taught was always deploy max flaps. As you can see, it isn't something that is for beginners though. With a little practice, you can pick up the basics, but every plane is different at the edge of the envelope, even the same model and year, so it is good to take the plane around a few times before trying the more complicated stuff.

 

I want to take my CT bush flying, but i am not quite ready for that. I am practicing on more and more rough terrain, and there is definitely a finicky art to it.

Link to comment
Share on other sites

I appreciate the spirit that's going into these exercises.

 

Way to go!

 

I would personally advise against making configuration changes during critical phases of flight, such as a soft field takeoff. Choose the appropriate flap setting (chosen by trial and error, if you like), but then set it and don't change it until established in a climb and well clear of the ground. Pilots have come to grief by futzing with flaps too soon, either settling back onto the runway too soon, or being distracted from the business at hand.

 

Finally, does not apply to Charlie Tango, but a great exercise is to play with partial power soft field techniques to simulate either the effects of high density altitude or the drag of soft terrain or both. In a C150 I would handle the throttle for the student and feed in about 2,000 rpm or so, so that getting airborn and then staying in ground effect to build up to Vx required quite a bit of technique - and time.

 

Best to have a lot of runway when playing with this, and an instructor along if you're not 100% comfortable.

Link to comment
Share on other sites

 

I would personally advise against making configuration changes during critical phases of flight, such as a soft field takeoff. Choose the appropriate flap setting (chosen by trial and error, if you like), but then set it and don't change it until established in a climb and well clear of the ground. Pilots have come to grief by futzing with flaps too soon, either settling back onto the runway too soon, or being distracted from the business at hand.

 

This is a rule of thumb. If you practice this takeoff style a lot and really experiment with your bird's envelope, then it becomes a judgement call. You really need to push your plane so you can feel how she likes to be handled, and when she's had too much.

 

I follow a slightly different modification to this rule: establish climb, then changes to configuration should be in a way that does not cause you to lose altitude, but a brief lower positive vertical speed is acceptable.

 

Here is how i recommend that you experiment with your envelope before you try it on the ground: experiment with flaps in the air, stalling with various flap settings and full power, so you can get a feel of what it is like. Now, simulate a takeoff (slow as you can, then do a power climb) and take notches of flaps out. The goal is to find what speeds are ideal to make sure you don't lose your positive vertical speed, but not slow enough to cause a stall with flap removal, and not fast enough to exceed your vfe for that setting. This range on my bird is actually extremely large, so rather than trying to remember exact numbers, i use a combination of feel, and use airspeeds that are closer to vfe.

 

Remember your loading too! These birds fly very differently with light vs heavy loading!

 

 

Finally, does not apply to Charlie Tango, but a great exercise is to play with partial power soft field techniques to simulate either the effects of high density altitude or the drag of soft terrain or both. In a C150 I would handle the throttle for the student and feed in about 2,000 rpm or so, so that getting airborn and then staying in ground effect to build up to Vx required quite a bit of technique - and time.

 

 

CTs with dynon ems or skyviews should have a manifold pressure gauge. Calculate what the MAP is for higher altitudes, and use that gauge to set power for practice.

Link to comment
Share on other sites

Maybe someone already mentioned this, but doesn't 40 deg in an SW actually induce more drag but not really any more lift vs. 30 deg? Wouldn't 30 deg essentially be better than 40 when trying to drag itself off the ground?

 

I have tested climbing with 30 deg to simulate a go around, and it was decent, not a real good rate of climb on paper, but held a fairly steep angle so I know objects could be dodged... haven't actually tested 40 deg back to back... just throwing it out there. 15 gets you off the ground pretty quick, I honestly assumed anything higher would work against you.. but at 6200ft field elevation things do work a bit different up there.

Link to comment
Share on other sites

I tried it yesterday. What a difference. I've done dozens of full-flap go-arounds (after touching down) so I am used to speeds at which to take out the flaps, etc. I just never had done one from a full stop. I use cruise pitch trim and just a bit if backward stick pressure until the front wheel lifts, but it seemed to me that all three wheels came off the ground at the same time.

 

With the 15 degree flap takeoff, you have to make sure you stay in ground effect to build up the speed for climb. With 30 and the engine at full power the propwash over the wings seems to generate more lift than ground-effect does.

 

Repost, I know.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...