Vne11. .You ask. . </font><blockquote><font size="1" face="Verdana, Arial, Helvetica">quote:</font><hr /><font size="2" face="Verdana, Arial, Helvetica">Could you please explain why you recommend not to hold the 210 on the ground? Why not leave it on the ground any longer than the book says for that acceleration.? . .</font><hr /></blockquote><font size="2" face="Verdana, Arial, Helvetica">OK, short version follows.. .As a result of the reflex wing configuration wing Angle of Incidence and high lift at relatively low airspeed wing of the C206, TO flap coupled with usually a fairly positive AoA due to the rear seat load, it is hard to keep it on the ground, even if you wanted to it will just fly off, unless you really want to practise driving a wheelbarrow. The difference between the TO speed and Best Rate climb speed is relatively low.. .That is with TO trim and hands off, these aircraft tend to be already at or approaching a level flight AoA at or around the speed/time you are ready to get airbourne any further increase in speed will just fly it off.. .. .OK now in general terms the C of P is also moving reawards with increase in speed so that is not helping us at this point and if we allowed the above situation to develop with increasing speed add the effect of camber of the flap the wheelbarrowing tendency increases and the force required to raise the nose and get the vectors pointing in the required direction increases, the elevator deflection required increases, the resulting profile and trim drag increases all at a time when we are on or close to being on the wrong side of the L/D curve. . .As an aside because of the torque at high power a lot of rudder is being carried at this low speed for directional control which equals higher drag.. .And the vertical stabiliser offset that provides the low drag solution to the problem in cruise flight is not yet fully effective. Go and have a look at the vertical stabiliser offset if you haven't already seen it by getting up on a step ladder at the front of the aircraft and look back down the dorsal surface of the aircraft over the wing down to the fin. You might also notice the engine offset from centreline.. .. .The gear being fixed is not a factor in this particular equation.. .. .So the balance of these forces is certainly not optimum when you fail to fly the aircraft faster than the numbers in the TO configuration in
any type. . .. .The C210 has by comparison a different wing section with out reflex leading edge and as a result of the gear configuration tends to sit "nose down" or in a relatively negative A o A which requires a more positive rotation to a positive A o A to become airbourne, add the C o P shift with TO flap and more rapidly increasing speed to the recommended 100KTAS best rate which is way way beyond the numbers required for TO and you can see that the forces described above are, relatively speaking, working much harder against you than in the C206.. .. .Landing way too fast is the other side of that coin and we all know what happens if you get it rel wrong and cant get the nose up because there is insufficient elevator authority. .. .Add to that the gear retraction sequence, remember drag is not a linear function with speed the sooner you can get it off the ground and cleaned up the faster it will get to that best rate speed and more rapidly increase the distance between yourself and the ground, which BTW is the whole object of the exercise in the first place.. .. .OK so now we can apply that simple L/D issues to the TO acceleration without introducing the complications of the above scenario. . .We all know how the L/D v AoA curve operates and it is pretty obvious that during the intial acceleration to the TO speed zero or a slightly negative A o A will not produce any lift and that pesky drag that comes with it and ensure that the acceleration will be at optimum for that segment of the TO.. .It becomes equally obvious that raising the nose to try and drag it off will have the opposite effect, drag being the operative word, and hanging about to get some extra speed is only going to consume extra runway, extra being the noperative word, either way once airbourne.. .The originally desribed after TO scenario is common to both until acceleration and final climb configuration is eventually achieved and the poor aircraft is maybe allowed to do what it does best despite your efforts to the contrary.. .. .That is fly the aircraft speeds computed at the weight and temp accurately and you will be rewarded with the performance advertised by the manufacturer.. .. .And while I'm at it the same applies to cruise.. .. .Fly it slower than the usual highest power settings available in the AFM in the usual old wives tale "engine saving mode" and you are actually achieving the opposite.. .
Remember the vertical stabiliser offset, the engine offset and the angle of incidence (between the fuselage and wing) v A o A are all set to produce the optimum speed lowest drag at THAT power setting anything
lower setting works against you, higher drag, engine working harder, lower speed, lower SAR , lower cooling conditions, higher fuel consumption and so it goes. The
"savings" are illusory.. .. .Fly accurately and by the numbers, this "macho grizzled aviator man against the elements feel and instinct" in day to day normal ops is just BS.. .. .Until you have built and sold as many aircraft as the manufacturer then leave the second guessing BS to the heroes in the aero club bar while you get on with being a well informed pro.. .. .What does this have to do with the big kids playground? Why do the manufacturers pump all this fuel backwards and forwards in long range cruise and why are winglets only really effective at high altiitude.. .I'll let you think that one through for yourselves. <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> . .But Checkboard, I or someone else is always around if you need help. <img border="0" title="" alt="[Wink]" src="wink.gif" />