• 

  gisburnuk
  January 19th, 2010 at 6:21 am

  Yes, Flight DHI 574 in indonesia. The crew correctly alligned the IRU’s at the gate however due to a fault the IRS’s failed in flight and loss navigation.
  The crew failed to correctly realign the IRU’s in flight (which for both 737′s requires selecting the IRS mode selectors to ‘ATT’. And maintaining wings level, constant airpseed for 30 seconds in order for the attitude displays to recover.
  Magnetic heading must also be updated periodically either on the CDU’s or directly on the overhead.

  The crew failed this process (ignoring the 30 seconds, wings level constant airspeed procedure) Due to this either autopilot cannot be used or engaged. The crew too busy problem solving and focused on the loss of navigation failed to notice the disengaged autopilot.
  The aircraft flying without input from either crew (and with no visible external horizon) slowly banked to the right. This exceeded 30 degrees of bank followed by voice activated ‘bank angle’ warnings, there to alert the crew of the impeding bank limit.
  The crew ignored this too and the aircraft remained banked for the duration. The crew inproperly recovered the aircraft and it exceeded 490 knots and crashed.

  Although the INS together with the both flight computers can determine the aircraft’s position (and follow a flightplan both laterally and vertically). It also determines the attitude of the aircraft (pitch, roll, yaw, etc) and conveys this information for ground speed (useful for taxi speed, ETA). Attitude, displayed in the EADI. And inertial vertical speed.
  However with a fault made aware by crews and both displays reverting to fail, the crew can rely on standby instruments that rely on external sensors rather than the INS fancy laser giroscope accelerometer thingy.

  For navigational purposes the crew can also revert back to the flightplan for navaid information. Tune the ADF, nav radios in order to fly towards NDB’s VOR’s and read DME to or away from stations. Which is enough for IR crew to determine releative position and navigate their way towards an airfield, holds, etc.

  Before takeoff, for aircraft equiped with this nice feature the IRU’s go through a position update on the ground (for the 737 NG’s). Or manual update for the 737 classics.
  With the aircraft tracking the runway heading FMC is able to update this information if it differs, and periodically and automatically when in the air.
  Radio updates, GPS updates for the NG’s etc. The IRU’s are known to drift and require this update, so it isn’t completely self reliant.

  Can you misalign the IRS?

  If the aircraft is moved whilst unpowered, when aligning the IRU’s the FMC will expect you to enter the position of the aircraft at the time it was unpowered, or last known position.
  If you continue to enter the wrong position of the aircraft (align light contunuing to flash) you can convince the FMC that your wrong position is correct.
  Some crews have be known to fly with pax with a misaligned INS, however with no fatalities. The FMC requires the aircraft to fly over physical naviads rather than those stored in the FMC to determine position.
  The route too needs to be varified by the crew, FMC route matches that on the flightplan. T/O runway heading matches that on the route when this isn updated through the application of T/O thrust or manually.

  The amercian airline’s 757 fatality occured when the crew selected the closest nav aid which was wrong, they flew towards it, into terrain and crashed. Both IRU’s working fine, both crews not so……..

• 

  vrrJT3
  January 19th, 2010 at 6:21 am

  Yes, the IRS and INS are two of the most hated government organizations ever, but I don’t think they’re directly responsible for any crashes.

• 

  John B
  January 19th, 2010 at 6:21 am

  can’t say i’ve heard of that as a cause although there have been a few accidents caused by pilots inputting wrong info into an ins or fms. the american airlines 757 in cali colombia comes to mind. selected the wrong waypoint and and the system took them into the side of a mountain. after that one, we began to uncouple the auto pilot from the flight director and watch what the command bars did when putting in an off airway waypoint before letting the airplane follow.

• 

  Robert G
  January 19th, 2010 at 6:21 am

  The problem with the old INS systems was that you had to manually program your start lat/long. If you took off and forgot to set it you either had to figure it out or land. Apparently a Korean Air 747 crew did this at one point. Turning back to set the INS was very expensive and the company announced that any crew that forgot to program the INS in the future would be fired.
  So Korean Air flight KAL 007 took off from San Francisco on 1983 and forgot to set the INS. Rather than return to SFO to reprogram it they tried to figure their current possition and program it from that. They were off. They were off and flew too far North. They were shot down by a Russian fighter after they entered Russian airspace. All 269 people died.

IRS Tax Archives

IRS Tax Search

• i know someone not paying taxes
• what is the max refund
• do i need to report when money from abroad
• tax delay
• 1201
• international student stimulus plan
• lottery

• Busso Ragusso @ How long can an attorney have to produce a will?: If there is no will, entitlement becomes Intestate....
• Kathi S @ How long can an attorney have to produce a will?: As his next of kin you can bring the estate to probate...
• wizjp @ How long can an attorney have to produce a will?: uh…why bother. Go directly to the probate office, be...
• v b @ How to file tax for my kid? file seprately or include in my tax return?: You file a return for him. The LTCG...
• Julia F @ How to file tax for my kid? file seprately or include in my tax return?: Child files own tax return using...
• taxreff @ How to file tax for my kid? file seprately or include in my tax return?: You need to file a return for him....
• chingon711 @ Obama: Don’t Extend Tax Breaks for Wealthiest: @NCMan28025 the stimulus you keep harping about...
• BertGriffin88 @ Obama: Don’t Extend Tax Breaks for Wealthiest: @LibertaerUeberAlles, Actually it was a Great...
• 2012er @ Obama: Don’t Extend Tax Breaks for Wealthiest: Oh fake president go back to your gig at the cia, and...