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marcom

Small quiz!

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Hi everyone!Here's an interesting scenario, which is done in the real sim aswell:Imagine a B737-600 departing KJFK and suddenly ALL your static ports are completely blocked up. This includes the captain's, the F/O's and all the backup ports.Now then, a couple of questions :-)a) What would be your first indication of this failure?:( What instruments are affected? (For simplicity, let's just look at the instruments on the forward panel, ie not the systems)c) How would you fly your departure? What would you use to determine the necessary information?d) Now a little tougher: what are two ways available to determine current altitude? (Without opening the outflow valves and reading cabin altitude!)That's enough for now :-)Regards,Mark

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>Hi everyone!>>Here's an interesting scenario, which is done in the real sim>aswell:>Imagine a B737-600 departing KJFK and suddenly ALL your static>ports are completely blocked up. This includes the captain's,>the F/O's and all the backup ports.>>Now then, a couple of questions :-)>a) What would be your first indication of this failure? Airspeed fails to Increase as you acclerate during the TO Roll.>:( What instruments are affected? (For simplicity, let's just>look at the instruments on the forward panel, ie not the>systems) Airspeed Trend Vector, Altimeter, Primary Flight Display, Nav Display>>c) How would you fly your departure? What would you use to>determine the necessary information? Now is where it get's tricky. 1. Have all the Necessary info tuned into ADF and VOR's. Use the Standby RDMI indicator to fly the departure route from the Nav Radio. Use the Standby Compass to fly headings if on vectors.Use Fuel Flow settings and Flap settings to determine airspeed - I have read that you can set a specific fuel flow on the 737 and this corresponds to a given speed. >d) Now a little tougher: what are two ways available to>determine current altitude? (Without opening the outflow>valves and reading cabin altitude!) One is to use the Radio Altimeter What did I score?

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Hi Mark,here's my answers....a) everything going dark due to the locus/dust/fly/groupie swarm that just appeared.:( not known, I only ever use landing view ;)c) pedal to the metal, gun engines and pull back stick at the end of the runway and hope for the best :Dd) once in the air, command FO to hang head out of the window to give rough estimate of hight, listen for pax screams as indication of being too low ;)Sorry, could't resist :-lol :-lol :-lol Regards,Bob Joneshttp://www.precisionmanuals.com/images/forum/devteam.jpgwww.precisionmanuals.combjones@precisionmanuals.comhttp://www.solentairvirtual.co.uk/images/santa_1.gif

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D) Stay at or below 2500ft so you can use the Radio Altimeter :(Damn you Mark :(I am slooooow

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Come on, you need to throw in the Volcanic Ash causing a double flameout then we are having real fun!Ray

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As well as using fuel flows, the pilot flying has to stay within a prescribed pitch envelope vs FF to ensure level flight.Cheers,JohnBoeing 727/737 Mechanic

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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.Regarding :("Airspeed Trend Vector, Altimeter, Primary Flight Display, Nav Display"Actually only one piece of information would be missing (or would be inaccurate) on the ND (IRS's are not coupled to the air data). What is that information?Again, the PFD is still available, but with info missing. What exactly?Airspeed trend vector - Actually, you'd still have the vector as the IRS's still provide acceleration. What you wouldn't have is the correct speed at the end of the vector.Regarding c)"1. Have all the Necessary info tuned into ADF and VOR's. Use the Standby RDMI indicator to fly the departure route from the Nav Radio. Use the Standby Compass to fly headings if on vectors."Your IRS's still work without a problem. No problem in the ND for navigation. (Although raw data is never a bad idea)"Use Fuel Flow settings and Flap settings to determine airspeed - I have read that you can set a specific fuel flow on the 737 and this corresponds to a given speed. "I don't know of other operators, but LH uses N1. You have a nice table in the QRH (quick reference handbook) with different weights and for different phases of flight (clb, crz, des) telling you which pitch attitude and N1 setting to fly.Regarding d)"One is to use the Radio Altimeter."100% correct. I just realized there was another way, although not every a/c will be able to do that.Also, the RA will only work below 2500 ft AGL. There are two more ways to determine altitude above 2500 ft!Regards,Mark

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Hi John,"As well as using fuel flows, the pilot flying has to stay within a prescribed pitch envelope vs FF to ensure level flight."Right! I just posted that crews have their QRH's out which provides them with a table for N1 and pitch for different phases of flight.I guess you could use FF but I only know the N1 technique.Mark

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LOL :-)Regarding altitude, you could always fly above the airfield and throw pax out the door. If you tell ATC the time of throwing a pax out they can tell you the elapsed time until ground impact and voila, a precise AGL altimeter (and you don't even have to set the pressure):-)(No, this is not one of the techniques I was mentioning above :-) )

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Okay so Mark had a head start on one technique. Two more to go :-)

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Recently I read an accident report for a 757 in South America that crashed into the sea, that suffered a similar set of problems.The cause was determined to have been the static ports were taped over during maintenance work, and nobody remembered to take the tape off.

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Yup, I read that report as well as the cockpit voice recorder transcripts. It seemed that the FOs PFD showed overspeed and the PFs PFD showed stall and they couldn't reconcile which was correct. Jeff

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To know your altitute above 2500' ask ATC. :-))Regards,Bjorn

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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.

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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

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>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

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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

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Correct!You could even get a negative airspeed :-)Also, during final approach you have to count with the overspeed warning going off.Mark

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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

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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

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