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 |
#21
|
|||
|
|||
At 07:30 29 December 2004, Eric Greenwell wrote:
I think the pilots trying this are not doing that, but instead rely on their airspeed to give them IAS. This does require calibration of the ASI for real accuracy. Actually the first post in this thread (from Mark) read: 'Has anyone done any work to develop a program that would look at some flight logs and determine what a particular glider's actual polar is?' This original idea has now morphed into a suggestion essentially to replicate the technique used by Dick Johnson and others, with the main difference being using the barometric altitude transducer in a flight computer instead of the mechanical altimeter(?). This might offer some improvement in accuracy, but is at least as complex to execute as the flight test techniques used for the past 40+ years. There are two main challenges with using flight logs only: 1) There is no good source for IAS, so you have to try to estimate it from GPS ground speed. 2) Typical soaring flights don't involve adequately calm vertical airmass movement and probably not constant enough airspeed to trust even long glides of many tens of miles. 9B |
#22
|
|||
|
|||
The different air masses, the different instruments
ect. ect. obviously lead to different results. Not being the physic's expert, I was just wondering if anyone has tried flight testing Sailplanes in a wind tunnel? Could you 'hard point' it and measure weights or lack of weight to get Polar info. Im sure boeing or MD has done something like that. I suppose that you may not get a direct glide ratio but could get a common start point that all gliders then could be compared to. Any comment from the mathematicians? At 14:00 29 December 2004, Andy Blackburn wrote: This original idea has now morphed into a suggestion essentially to replicate the technique used by Dick Johnson and others, with the main difference being using the barometric altitude transducer in a flight computer instead of the mechanical altimeter(?). This might offer some improvement in accuracy, but is at least as complex to execute as the flight test techniques used for the past 40+ years. There are two main challenges with using flight logs only: 1) There is no good source for IAS, so you have to try to estimate it from GPS ground speed. 2) Typical soaring flights don't involve adequately calm vertical airmass movement and probably not constant enough airspeed to trust even long glides of many tens of miles. 9B |
#23
|
|||
|
|||
Andy Blackburn wrote:
This original idea has now morphed into a suggestion essentially to replicate the technique used by Dick Johnson and others, with the main difference being using the barometric altitude transducer in a flight computer instead of the mechanical altimeter(?). This might offer some improvement in accuracy, but is at least as complex to execute as the flight test techniques used for the past 40+ years. There are two main challenges with using flight logs only: 1) There is no good source for IAS, so you have to try to estimate it from GPS ground speed. This data is available from various instruments, like the Cambridge 302 that I use. For the 302 it's actually the TAS, which could be combined with the air temperature and pressure altitude to compute the IAS. The TAS and temperature are not recorded in the 302 flight log, unfortunately, but they could be recorded by the Ipaq connected to it and inserted in the flight log it keeps, and this log used for the analysis. 2) Typical soaring flights don't involve adequately calm vertical airmass movement and probably not constant enough airspeed to trust even long glides of many tens of miles. I think this is a show-stopper, even if the IAS is available in a flight log. -- Change "netto" to "net" to email me directly Eric Greenwell Washington State USA |
#24
|
|||
|
|||
At 20:00 29 December 2004, Cliff Hilty wrote:
I was just wondering if anyone has tried flight testing Sailplanes in a wind tunnel? Could you 'hard point' it and measure weights or lack of weight to get Polar info. Hey Cliff, A wind tunnel would allow you to measure lift and drag forces directly at various speeds, angles of attack and flap settings. From this you could generate a polar for any weight. This would be the most accurate way to generate a polar I believe because it is under lab conditions with highly calibrated instrumentation. Of course you'd need a big wind tunnel like the NASA Ames 80'x120' low-speed tunnel. You can rent it out, but I bet it's expensive. To cover all the speeds, flap settings and weights you'd need several dozen test points, which would require a few hours in the tunnel. http://windtunnels.arc.nasa.gov 9B |
#25
|
|||
|
|||
At 20:00 29 December 2004, Eric Greenwell wrote:
Andy Blackburn wrote: 1) There is no good source for IAS, so you have to try to estimate it from GPS ground speed. This data is available from various instruments, like the Cambridge 302 that I use. For the 302 it's actually the TAS, which could be combined with the air temperature and pressure altitude to compute the IAS. The TAS and temperature are not recorded in the 302 flight log, unfortunately, but they could be recorded by the Ipaq connected to it and inserted in the flight log it keeps, and this log used for the analysis. Neat idea - is that a configuration item on the 302 and/or WinPilot, or do you need to write software/firmware to make it happen? Of course you'd still need to calibrate the 302 IAS transducer for each sailplane type, but at least then it would automate the data capture for the kinds of performance testing Dick Johnson does. Maybe he already has a rig to do this, but maybe not. It would also allow collecting data from more than a single test subject since anyone who could take a high tow on a calm day and hold a constant airspeed for more than 5 minutes could contribute a test point. Of course here I'm assuming that all 302s and sailplanes of a particular type with the same pneumatic setup have similar airspeed errors, which may or may not be true. 9B |
#26
|
|||
|
|||
Andy Blackburn wrote:
The TAS and temperature are not recorded in the 302 flight log, unfortunately, but they could be recorded by the Ipaq connected to it and inserted in the flight log it keeps, and this log used for the analysis. Neat idea - is that a configuration item on the 302 and/or WinPilot, or do you need to write software/firmware to make it happen? I don't know about Winpilot, but it's not part of SeeYou Mobile. I think it could easily be added by SeeYou and included in the Ipaq flight log it can already keep, and I've suggested it to SeeYou. It's just another data "sentence" that the 302 can send out. Of course you'd still need to calibrate the 302 IAS transducer The sensor could be (probably is already) calibrated by Cambridge and other labs when it is calibrated for flight recorder use. for each sailplane type, You wouldn't have to measure your pitot/static system if you were interested only in your glider, and not in comparing the data with data from other gliders; for example, if you just wanted to maximize your use of the flaps and speeds. but at least then it would automate the data capture for the kinds of performance testing Dick Johnson does. I'm sure he does use an automated logger of some kind. I don't think he's used a "vibrating panel" for quite a while! -- Change "netto" to "net" to email me directly Eric Greenwell Washington State USA |
#27
|
|||
|
|||
at least then it would automate the data capture for the kinds of performance testing Dick Johnson does. "Eric Greenwell" I'm sure he does use an automated logger of some kind. I don't think he's used a "vibrating panel" for quite a while! I the spring of 2003 Dick Johnson when he tested my glider he still used the hard ware he has been using for a long time. A vibrator for the Panel, he calibrates the airspeed indicator and the altimeter. He uses his own instruments and takes notes of temperature and as he flies trough 500ft timed intervals. He is able to do 3 to six speeds for each flap setting on one flight from 12000ft. In my case he made two flight. The other aids are a stop watch, a note pad and at least two if not three pencils. I would be able to provide you with a copy of the numerical data sheet. Regards Udo |
#28
|
|||
|
|||
Udo Rumpf wrote:
I'm sure he does use an automated logger of some kind. I don't think he's used a "vibrating panel" for quite a while! I the spring of 2003 Dick Johnson when he tested my glider he still used the hard ware he has been using for a long time. A vibrator for the Panel, he calibrates the airspeed indicator and the altimeter. He uses his own instruments and takes notes of temperature and as he flies trough 500ft timed intervals. He is able to do 3 to six speeds for each flap setting on one flight from 12000ft. In my case he made two flight. The other aids are a stop watch, a note pad and at least two if not three pencils. I would be able to provide you with a copy of the numerical data sheet. I was sure I'd read/heard he was using an electronic logger, at least at one time. Did he mention if he'd tried one, or if some of the pilots assisting him used one? -- Change "netto" to "net" to email me directly Eric Greenwell Washington State USA |
#29
|
|||
|
|||
The Zander flight computer performs a constant L/D calculations throughout a
flight. The L/D is presented numerically on the screen. All you need to do is note the L/D, flap setting and speed at any particular time. David "Mark Zivley" wrote in message m... We all know what the manufacturer's polars look like, but what about our individual planes. Has anyone done any work to develop a program that would look at some flight logs and determine what a particular glider's actual polar is? At one point Ball was making a vario system that would determine the aircraft's polar over time just by flying. For someone who already had some algorithms for computing wind from ground track drift during thermals could take this info and then be able to back figure from GPS ground speed what the IAS was during a particular phase of the flight. By isolating longer sections of cruise flight at varios airspeeds it should be do-able. Question is, has it been done. Mark extra "hot" in the address to delay the spammers... |
#30
|
|||
|
|||
Udo Rumpf wrote:
I'm sure he does use an automated logger of some kind. I don't think he's used a "vibrating panel" for quite a while! I the spring of 2003 Dick Johnson when he tested my glider he still used the hard ware he has been using for a long time. A vibrator for the Panel, he calibrates the airspeed indicator and the altimeter. He uses his own instruments and takes notes of temperature and as he flies trough 500ft timed intervals. He is able to do 3 to six speeds for each flap setting on one flight from 12000ft. In my case he made two flight. The other aids are a stop watch, a note pad and at least two if not three pencils. I would be able to provide you with a copy of the numerical data sheet. Eric wrote I was sure I'd read/heard he was using an electronic logger, at least at one time. Did he mention if he'd tried one, or if some of the pilots assisting him used one? I did ask him if loggers are helpful to him and he said no. That would indicate he may have tried using it as an aid. Udo |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
RAF Blind/Beam Approach Training flights | Geoffrey Sinclair | Military Aviation | 3 | September 4th 09 06:31 PM |
AOPA Stall/Spin Study -- Stowell's Review (8,000 words) | Rich Stowell | Aerobatics | 28 | January 2nd 09 02:26 PM |
new theory of flight released Sept 2004 | Mark Oliver | Aerobatics | 1 | October 5th 04 10:20 PM |
Flight Simulator 2004 pro 4CDs, Eurowings 2004, Sea Plane Adventures, Concorde, HONG KONG 2004, World Airlines, other Addons, Sky Ranch, Jumbo 747, Greece 2000 [include El.Venizelos], Polynesia 2000, Real Airports, Private Wings, FLITESTAR V8.5 - JEP | vvcd | Piloting | 0 | September 22nd 04 07:13 PM |
AmeriFlight Crash | C J Campbell | Piloting | 5 | December 1st 03 02:13 PM |