Malaysian Air 370 (MH 370) Im not so annoyed with the wild speculation, rather the so-called subject-matter-experts (SMEs), who are talking about the flight systems, etc. First, Im not a pilot or an engineer, but I think I can at least add some context to the discussion given my 34 years of aviation experience (mostly in operations). To begin, radar... Radar was developed in the 1940s and while proven is not precise and has limits, including terrain and line-of-sight factors. The effective range of radars is approximately 250 nm, (especially coastal radars). No radars over the ocean. (ATC and airlines use position reports). First a bit of physics. Radar uses high energy (electromagnetic energy pulses). That energy reflects/returns (ECHO) to the radar set (dish). This is a primary surveillance radar (PSR) and provides basically distance and direction, (see right bottom graphic). In the photo inset on the bottom left, thats the lower portion of the radar head. We also refer to PSR as non-cooperative as it doesnt need anything on board the aircraft; the mass of the object is picked up by the ECHO. Secondary Surveillance Radar (SSR), or the upper portion (fence like structure on top of the radar), is cooperative surveillance. SSRs send out an interrogation and the aircraft transponder, (typically a Mode-S select transponder) provides a coded reply. Hey Im MH370 a B777 at x altitude. There is also some other information derived from a unique hex code 24-bit ICAO address. Mode S transponders broadcast in the 1090 spectrum. These transponders are also used in Traffic Conflict Alert Systems (TCAS). By roughly 2020, aircraft like the B777 will be required to upgrade transponders to 1090 extended squitter (ES) as the world switches to Global Navigation base surveillance (leveraging GPS to precisely locate the aircraft vs. radars limitations) or Automatic Surveillance Broadcast (ADS-B). My company, Exelis, is installing the ADS-B constellation here in CONUS, Hawaii, Guam and the Caribbean). It is likely that MH370 was ADS-B equipped, which provides more precision but is a cooperative technology, (without the transponder on the target cannot be seen w/o PSR). So when the transponder was switched off, its possible the MH aircraft was still visible via PSR, (it would just be a blimp with no other information (distance/bearing) since there is no SSR). I suspect the aircraft did not go north-northeast given that it would overfly coastal areas and land areas, where PSR radars could have picked it up. Most certainly, an unidentified target that didnt respond to ATC would have be intercepted. The B777 is a sizeable target given its mass. If the SSR was turned off after PSR coverage was lost, it would have been picked back up as it crossed back over Malaysia and proceeded westerly (over the Indian ocean). It should have still been intercepted as an unknown target. That would not happen here in the USA. ACARS--- Aircraft Communication Addressing and Reporting System, has been aboard aircraft since the late 1970s. Think of it as email or text to/from the aircraft. For example at American, once the final passenger count is entered, cargo/fuel information is updated, ACARS sends a message to the flight deck with the take-off power settings and trim settings. Dispatch can send messages such as weather updates and amended flight plans, etc.. With technology and more sophisticated aircraft like the B777, ACARS is also a data-link system that can provide real-time telemetry on engine performance and other systems via a system called referred to as FDAMS (Flight Data Acquisition & Management). Turning off ACARS would kill this High Frequency (HF) link to ground and satellite-based systems. Because aircraft like the B777 are transoceanic there are areas that dont have radio coverage (and radar as previously explained), so SATCOM systems are on-board. The SATCOM system is designed to provide position reports (X,Y,Z = lat, lon & altitude) via ACARS at a certain interval, (Im not sure but I believe its every quarter hour). SATCOM time is expensive. So even though the ACARS was shut off, the on-board systems were still pinging the communication satellites in the vicinity. This is how they were able to determine that the aircraft flew for several hours after communications and surveillance were lost. Engineers are likely using more physics to triangulate the aircrafts position based upon satellite pings, altitude and speed. I dont believe this was a catastrophic failure of the aircraft based upon the changed course and sequential shutdown of the transponder and ACARS, plus the satellite reports continued for several hours. There would have been a mayday/distress call I believe. Also had someone attempted to break-in, the pilots should have been able to make a distress call or squawk a hijack code prior to transponder being switched off. I too suspect flight crew (one or more) involvement. I dont believe the aircraft landed anywhere, I think it crashed west of its last calculated track somewhere in the Indian Ocean. I only hope we can pick up the Emergency Locator Transmitter (ELT) beacon before its battery dies (10-14 days). I encourage my commercial pilot friends to add too or respectfully refute my facts. I feel better now!
Posted on: Wed, 19 Mar 2014 05:19:55 +0000
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