|
| If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|||||||
|
|
Thread Tools | Display Modes |
|
#151
May 6th 08, 04:47 PM
posted to rec.aviation.piloting
|
|||
|
|||
limit of trim = limit of travel?
wrote in message
... On May 5, 5:55 pm, WingFlaps wrote: Does the elevator lift force and stall angle reflect trim setting at all? Cheers Probably to some rather minor degree. The government just demands that the airplane behave in certain ways in various configurations and maneuvers, so the designers have to build their airplanes to fit within those specs. An elevator should never stall before the wing, for example, or the whole machine could flip over onto its back. The rising tail, rising because the stab/elevator stalled, would experience an even higher AOA as it rose and things would get very nasty. The certification guys want the nose to drop gently as the wing stalls, which couldn't happen if the stab let go too soon. Some airplanes (I.E. Ercoupe) had limited up-elevator to prevent wing stall and therefore the stall/spin scenario that killed so many in the '40s and '50s. The nose didn't drop because the wing stalled but because the stab/elevator ran out of nose-up authority. It could easily have been modified to get the stall. There was plenty of area there. Only problem was that guys would get slow on final and pancake into the ground and break their backs with compression fractures. Don't necessarily need to stall to get killed. Actually, the more powerfull tail was eventually added, as the Cadet, after Mooney bought the type design rights and type certificate. IIRC, it was then touted as a solution to the perceived shortcommings in pilot training, in much the same way as the Tomahawk--which arrived a few years later. My recollection is that sales were poor, and the Cadet is now all but forgotten... Peter 
|
|
#152
May 6th 08, 04:57 PM
posted to rec.aviation.piloting
|
|||
|
|||
|
limit of trim = limit of travel?
"WingFlaps" wrote in message
... Dan, you keep trying to pick up the wrong end of the stick. I'm not talking about certification. For example, in the FARs does it describe how the stabilator chord changes with trim positions? Certification results from practical demonstrations of plane handling and flying not theoretical aeronautical discussions -or is that not so? Cheers Please forgive my for seeming to nit pick, but... How does one talk about presumed abnormalities in the operation of type certified aircraft, within the certified parameters, and then appear to separate that discussion from the engineering and testing which must have resulted in the certification? Peter (Starving for enlightenment)
|
|
#153
May 6th 08, 04:57 PM
posted to rec.aviation.piloting
|
|||
|
|||
|
limit of trim = limit of travel?
|
|
#155
May 6th 08, 05:01 PM
posted to rec.aviation.piloting
|
|||
|
|||
|
limit of trim = limit of travel?
WingFlaps wrote in
: On May 7, 12:56*am, Stealth Pilot wrote: On Mon, 5 May 2008 23:54:37 -0700 (PDT), WingFlaps wrote: On May 6, 3:36*pm, Bertie the Bunyip wrote: WingFlaps wrote innews:4c947801-0112-4fa1-92e7-09 : OK, then if the AOA of the stabilator is constant, and the elevator angle is constant, why does the lift reduce when the trim tab is deflected in the opposite direction? because the elevator angle isnt bloody constant. what is constant is the stick force which you maintain at the same pressure by unconsciously moving the stick as you change the trim tab position. It's as I said, the effect is as if the _effective_ area is reduced. no it bloody isnt. the area remains the same the lift force is what varies and guess what, that's why the tailfeathers have the hinges in the middle. You could say that CL is altered but then it gets more messy as you have to consider different CL's and areas for each section of the stabilator. It's much simpler to just subtract the area taken by the trim from the calculation and that will give a very good first order approximation for longitudinal stability calculations. you have basically started out with a faulty understanding and for the last 100 posts have misinterpreted everything written because you keep relating the information to the original faulty premise. Nope. I understand it perfectly. As defined in any good book on aeronautical design, stabilator effectiveness is _defined_ by the horizontal tail volume coefficient which is the product of tail moment and area divided by the wing area and it's mean chord. From the style of you reply I can see you will have a hard time understanding this this it really is correct -look it up. I understand what you are saying perfectly. You might think it's a handy way to look at the problem, but it's simpoistic and incorrect.. End of story. Bertie
|
|
#156
May 6th 08, 05:08 PM
posted to rec.aviation.piloting
|
|||
|
|||
|
limit of trim = limit of travel?
|
|
#157
May 6th 08, 07:01 PM
posted to rec.aviation.piloting
|
|||
|
|||
|
limit of trim = limit of travel?
On May 6, 9:40 am, WingFlaps wrote:
Dan, you keep trying to pick up the wrong end of the stick. I'm not talking about certification. For example, in the FARs does it describe how the stabilator chord changes with trim positions? Certification results from practical demonstrations of plane handling and flying not theoretical aeronautical discussions -or is that not so? The FARs don't care how the chord changes. They don't care how the engineer achieves the flying qualities and strength they demand for certification. They just set certain parameters that must be met, and the engineers design an airplane that complies with those parameters. If the trim tab damaged the effectiveness of the elevator so that the control surface stalled, or lost authority to the point that the parameters could not be met, certification would not take place. Period. Your arguments are specious. Neither the FAA nor any foreign national governing body is going to get into the minutiae of design specifics. There's no time and no need. Or did you want to pay more taxes and user fees and a higher price to buy or rent an airplane, just to achieve through endless detail what is already achieved through mandated performance and strength limits? Dan
|
|
#158
May 6th 08, 09:15 PM
posted to rec.aviation.piloting
|
|||
|
|||
|
limit of trim = limit of travel?
On May 7, 6:01*am, wrote:
On May 6, 9:40 am, WingFlaps wrote: Dan, you keep trying to pick up the wrong end of the stick. I'm not talking about certification. For example, *in the FARs does it describe how the stabilator chord changes with trim positions? Certification results from practical demonstrations of plane handling and flying not theoretical aeronautical discussions -or is that not so? * * * * * * The FARs don't care how the chord changes. They don't care how the engineer achieves the flying qualities and strength they demand for certification. They just set certain parameters that must be met, and the engineers design an airplane that complies with those parameters. * * * *If the trim tab damaged the effectiveness of the elevator so that the control surface stalled, or lost authority to the point that the parameters could not be met, certification would not take place. Period. Your arguments are specious. There are lots of factors that may _promote_ a surface stall (e.g. rivet heads) but that doesn't mean the surface is not going to do it's jub well enough to let the plane fly and pass the certification test. It's similar to the (better known) idea that rivet heads may promote flow separation -but that does not mean that riveted planes can't pass certification does it? Understanding the effect of the trim tab on the elevator may prevent the mistake of thinking it ihas _no_ effect on elevator performance. It may be a philosophical discussion but that does not mean it's specious. Cheers
|
|
#159
May 7th 08, 12:43 AM
posted to rec.aviation.piloting
|
|||
|
|||
|
limit of trim = limit of travel?
On May 6, 2:15 pm, WingFlaps wrote:
Understanding the effect of the trim tab on the elevator may prevent the mistake of thinking it ihas _no_ effect on elevator performance. It may be a philosophical discussion but that does not mean it's specious. Oh, _well,_ then, let's just say that the trim tab deletes a little of the elevator's effectiveness, but not enough to matter, and leave it at that. Dan
|
|
#160
May 7th 08, 11:18 AM
posted to rec.aviation.piloting
|
|||
|
|||
|
limit of trim = limit of travel?
On May 7, 11:43*am, wrote:
On May 6, 2:15 pm, WingFlaps wrote: *Understanding the effect of the trim tab on the elevator may prevent the mistake of thinking it ihas _no_ effect on elevator performance. *It may be a philosophical discussion but that does not mean it's specious. * * Oh, _well,_ then, let's just say that the trim tab deletes a little of the elevator's effectiveness, but not enough to matter, and leave it at that. Yea, it may, under the conditions I specified. Yes, let's end this fun discussion as there's not much left to be said. Cheers
|
| Thread Tools | |
| Display Modes | |
|
|
Similar Threads
|
||||
| Thread | Thread Starter | Forum | Replies | Last Post |
| The Sky is Their Limit | [email protected] | Soaring | 7 | November 13th 06 02:44 AM |
| speed limit in class B | Andrey Serbinenko | Piloting | 0 | July 23rd 06 04:05 AM |
| Pegasus life limit | Mark628CA | Soaring | 2 | March 30th 06 10:37 PM |
| Aft CG limit(s) | Andy Durbin | Soaring | 13 | November 26th 03 05:10 AM |
| Pushing the limit | Dan Shackelford | Military Aviation | 20 | September 14th 03 10:27 PM |
Linear Mode
