December 18, 200322 yr Let's see, you'd lose TAS and wind direction/speed on the ND, right?Lee Hetherington (KBED)http://www.precisionmanuals.com/images/betaimg.jpg
December 18, 200322 yr Hi jeff,yeah, it's in a book I got as a gift of Cockpit Voice recordings. One of the most remarkable is the United DC-10 at Sioux City.
December 18, 200322 yr Author Commercial Member Right on!Both indications would show rediculous data. I have seen wind indications (in this situation) of a 300 kts tailwind :-)A very strong jetstream at 3000 ft :-)Mark Mark Foti Author of aviaworx - https://www.aviaworx.com
December 18, 200322 yr >Hi Mark!>>Regarding a)>>"Airspeed fails to Increase as you acclerate during the TO>Roll.">I don't want to give out the precise answer yet, but that's>not the only clue. It would be if your pitot was stuck, but>not if your static is blocked.>If the static ports are blocked, the altimeter will "freeze" at whatever altitude it was indicating at the moment the blockage occured.At the same time, the airspeed indicator will start acting like an altimeter. Assuming actual true airspeed remains constant, indicated airspeed would drop as the aircraft climbs above the altitude where the blockage occured, and would increase as the aircraft descends.If the aircraft climbed high enough, indicated airspeed would drop to zero, even if the aircraft is actually moving a high TAS.By contrast if the static blockage took place at a high altitude, IAS would eventually increase beyond redline as the aircraft descended, even if it were (somehow) standing still and not moving forward at all.Jim Barrett Jim BarrettLicensed Airframe & Powerplant Mechanic, Avionics, Electrical & Air Data Systems Specialist. Qualified on: Falcon 900, CRJ-200, Dornier 328-100, Hawker 850XP and 1000, Lear 35, 45, 55 and 60, Gulfstream IV and 550, Embraer 135, Beech Premiere and 400A, MD-80.
December 18, 200322 yr Author Commercial Member Aha, but your altimeter encoder, which the transponder uses to send altitude data to ATC, uses the same erroneous data. Therefore, it is extremely important to notify ATC that the altitude they see you at is wrong and that you can not confirm your altitde so that they clear all traffic away from you.Regards,Mark Mark Foti Author of aviaworx - https://www.aviaworx.com
December 18, 200322 yr Author Commercial Member Correct!You could even get a negative airspeed :-)Also, during final approach you have to count with the overspeed warning going off.Mark Mark Foti Author of aviaworx - https://www.aviaworx.com
December 18, 200322 yr That makes perfect sense. If you had a GS of 300kts and a IAS=TAS=0, the computer would assume you are a hot air balloon with all your GS coming from a tailwind. Not exactly the correct conclusion.Lee Hetherington (KBED)http://www.precisionmanuals.com/images/betaimg.jpg
December 18, 200322 yr Yes, in a thrust producer the fuel flow=thrust required=drag. Just look at the graph and a specific fuel flow will give you 2 airspeeds..1 in the region of normal command (above minimum drag) and 1 in the region of reversed command. Just remember that the graph shifts with weight changes, configuration changes, and altitude changes. For a climb I suppose you can use the equation RC=101.3*V(Ta-Tr/W) and solve for V. Or you could just shoot for maximum climb angle (which occurs at minimum drag) and use that airspeed.Im not sure if this is what they would really do. Im just using my basic knowledge of aerodynamics.Keith Yingling
December 18, 200322 yr I knew a guy that was in that crash. He was sitting near the section that split off. He survived but the two people next to him didnt. He rolled 300 yards beside the runway in the grass. he said the only thing he remembered was a big fire ball coming toward him. Didnt wake up for several months. He's a millionaire now, of course.Keith
December 18, 200322 yr Author Commercial Member In these types of situations, any equation a pilot has to calculate would not be very helpful.All I know is that the table provides a N1/pitch attitude for a given weight for a specific phase for a specific altitude.A resulting error should be pretty small, as you already have to interpolate between different weights and thus the N1 won't be 100% correct. Of course, you won't be able to maintain 0 VS even if you did set the N1 100% correctly and fly the exact pitch attitude as you still have to take the weather into account.But it will be precise enough not to fly into terrain and to make it to the IAF where you can fly a normal ILS approach where an altimeter is not required (of course, normally, it is required to perform the required crosschecks but in an emergency you simply have to assume that the darn thing works :-), and you still have the two ways determining altitude which haven't been covered yet :-) )Regards,Mark Mark Foti Author of aviaworx - https://www.aviaworx.com
December 18, 200322 yr G'day For altitude i think you should be able to access the ALT info from the GPS system via the FMC as position data.All IFR approved GPS's have true ALT data available via a position page.Don't know the other one though.Have fun
December 18, 200322 yr Author Commercial Member Exactly!That is indeed one way of getting altitude information!Now what's the other way?Regards,Mark Mark Foti Author of aviaworx - https://www.aviaworx.com
December 18, 200322 yr Author Commercial Member Hi Eker!DME would be a way, yes, but it's very unprecise. Also, you'd have to be right on top to determine altitude.OAT. I guess you mean SAT as you don't have an OAT indication. That would work, but for that you'd need the ISA deviation for the current location and you'd have to assume that there is no inversion where you currently are.I don't really understand your third proposal. Could you ellaborate on this?There is one more technique no one has mentioned yet. I'll post it later on.Mark Mark Foti Author of aviaworx - https://www.aviaworx.com
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