777 Emergency Descent Mode?
 

Barit asked the question in post #2932

Can anyone with technical knowledge of the MAS 777 FMS answer the question definitively - did MH370 have an Emergency Descent Mode or not?

Newer business jets have it fitted.

IAN

With such a powerful "ping" they could already trawled the area and located the wreck

Like you idea for the bean counters make then feel the effects of their decisions, what is that cost compared to the original price of the plane , less than peanuts.

faraday cage
 

Would the 406 ELT work inside a faraday cage, with no ability for gps signal reception or comms with sarsat?


Same could be asked of a piece of coax terminated in a dummy/artitifical load.


We use shielded rooms to service sensitive equipment, while hundred KW transmitters run outside.
We use shielded rooms at primary airports to service avionics, when the door is shut with double screened rooms, a cage with a cage nothing gets in not even the nearby NDB.


When you shut the door it shuts out the world,


WIII SAYS
Faraday cages cannot block static or slowly varying magnetic fields, such as the Earth's magnetic field (a compass will still work inside). To a large degree, though, they shield the interior from external electromagnetic radiation if the conductor is thick enough and any holes are significantly smaller than the wavelength of the radiation.




That's why you can look through your microwave door and not get zapped.


However a slight amount fo escaping radiation from case or equipment direct l ine of sight to a satellite maybe only in order of microwatts. anything is possible...

I always tell the story of my aircraft where some rain got in and dripped into the external ELB switch, just enough to allow electricity to conduct through the switch
The eleb light was not on but I got called out of bed at 400am to go to the airport as using a hand held thay had traced it to my plane.
A satellite and subsequent overflying jets had narrowed it to my home base.
The elb was putting out microwatts

Previous graphic shows Oz with 1 search ship and no helos assigned.
Did it sail without a helo ? Maybe none available in Perth for the navy on short notice.

Beancounting is neither here nor there. ELT's are lifesaving equipment that transmit on internationally standardised frequencies to enable life saving, not underwater wreck recovery.

ELT's - more info
 

Too add to the ELT info. I don't know the specifics of the 777 ELT's (some others on here have more info on this). However, the following is general information that will apply to detection and localization of them.

Modern ELT's transmit a periodic 5 watt data burst on 460.25, which is received by low earth orbiting SAR satellites. They also transmit a lower power continuous "whoop-whoop" on the old ELT frequencies of 121.5 and 243, for direction finding during the final phase of localization.

The 5 watt ELT signal, even inside an aircraft like a 777, should be detectable at quite a range, even with the shielding effect of the aircraft hull. I suspect the SARSAT's would pick it up.

ELT's are frequently disabled by crashes (as mentioned by another poster earlier). The antenna can be severed, reducing the range to tens of meters, or the ELT can be destroyed. They are really designed for survivable crashes. They often have G-switches. The batteries are supposed to last a couple of days. I once found an older (121.5) ELT in an aircraft that had crashed and burned on landing - the heat from the fire had moved the ELT well off frequency, but it was still whooping.

Until 2009, COSPAS/SARSAT monitored 121.5 and 243.0. Now they only monitor 406.025. The latter frequency is sent with much higher power and better carrier stability, so the ELT location, derived from doppler as perceived by the satellite, is more accurate than with the older ELT's. ELT's on 463.0 are now monitored by both geosynchronous satellites and low earth orbit satellites (which do doppler processing, decode the digital beacon, and transmit the results to ground stations). Note that the geosynchronous satellites can provide near instantaneous notification of ELT activation, but may not give position.

Newer ELT's may also have GPS's and thus transmit GPS coordinate. They are also registered, so reception of a signal identifies the ELT. I once found one which was also shouting MAYDAY on 121.5 (recorded voice), making us think there was a pilot in distress, when in reality it was an accidentally triggered ELT in an parked aircraft. Grrr.


I suspect an ELT in the 777, built into the vertical stabilizer, might have much higher crash resistance than those in smaller aircraft, and the tail may stay intact.

This would be an extremely weak effect. Even the baseline for GR time dilation between Earth's surface and the satellite in a geosynchronous orbit is ~50 microseconds/day (5*10^-10), equivalent to frequency shift of just 1 Hz in the microwave band. Fluctuations in the geoid aren't going to be visible without sophisticated equipment.

Doppler analysis of flight MH370
 

Once the trigonometry of flight MH370 has been figured out, it is possible to do a few calculations to assess the effect of the airplane's speed on the frequency of the signals it used to communicate with the Inmarsat-3F1 satellite. I have assumed that MH370 flew for 6.83 hours along a great circle route from its last known position to a point over the debris field. I have also assumed that it flew at a constant airspeed of 850 kilometers per hour. It is possible to calculate the velocity of MH370 (both speed and direction) at every point along this route. It is then possible to divide this velocity into two components, one along the line-of-sight to the Inmarsat and the other at right angles to this line-of-sight. The following graph shows the component of MH370's velocity along the line-of-sight. At the start of its silent flight, MH370 was flying at a speed of 219.3 kph (kilometers per hour) directly towards the satellite and 821 kph directly perpendicular to the line-of-sight. Therafter, the airplane flew in a direction further and further away from the satellite, and the component of the velocity along the line-of-sight decreased. By the time the airplane reached the debris field, it was travelling radially away from the satellite at a speed of 500.5 kph and directly across the satellite's field-of-view at a speed of 687 kph.
http://www.mh370.ca/Radial_speed.gif
We have all heard the Doppler effect. It affects radio waves in pretty much the same way as it affects sound waves. The Doppler effect arises when there is relative motion between the source of the wave (a fire truck or MH370, for example) and the receiver (you or the satellite, respectively). The Doppler effect does not change the speed at which the waves travel. Instead, it changes the apparent frequency. The frequency of the wave transmitted by the source is not the same as the receiver heard by the receiver. When the source and receiver are travelling towards each other, the apparent frequency received is higher. The degree to which the apparent frequency is raised or lowered depends on the relationship between the speed with which the wave travels through the material between and source and receiver and the relative closing speed between the two. In the case at hand, the speed of the wave is the speed of light: 1,080,000,000 kph. The relative closing speed (above graph) ranges from 219.3 kph at the start of the silent flight to negative 500.5 kph (negative closing speed resulting in a lowering of the frequency) at the end. Expressed as a percentage of the speed of light, these two closing speeds are 219.3 / 1.08E9 = 0.00002% and -500.5 / 1.08E9 = -0.00005%.

These are very small shifts in frequency. Big passenger airplanes use at least four frequency ranges, called "bands", in their communications. When the pilots talk to ground control, they use frequencies a little bit above 100MHz, just above your FM radio. The "Primary Channel Worldwide" for the ACARS reporting system is 131.55MHz. Much has been heard in the aftermath of MH370 about the use of satellites to relay the ACARS information, but the bulk of ACARS messages do not pass through satellites. When airplanes fly over land, the ACARS communications go over a land-based, cheaper network. The transponders about which we have heard so much are sent at frequencies near 1030MHz. When airplanes are far out over the sea, and communicate their ACARS data through satellites, they use even higher frequencies. The Inmarsat-3F1 satellite transmits at 1630MHz and receives at 1530MHz. One assumes that the Inmarsat study into the Doppler effect used data exchanged at these higher frequencies. Since the airplane's speed is such a small fraction of the speed of light, the percentage shift in frequency will be almost proportional to the relative speed percentages described above. The following graph shows the frequency shift (in Hz) which would be experienced by a continuous radio wave transmitted at 1600MHz by MH370 to the satellite during its silent flight.
http://www.mh370.ca/Frequency_shift.gif
These frequency shifts range from an increase of about 325Hz to a decrease of about 750Hz. I will say this: the Inmarsat people must be very good engineers to detect such small changes in a 1600MHz carrier, particularly when their radio equipment was probably designed to overcome and ignore such noise.

GQ2 . . .
 

But it's hard to conceptualize any non experienced B777 pilot disabling TXP & ACARS, turning, descending, and steering the airplane in an evasive flight profile towards the middle of a remote ocean without attempting to communicate if there was a mechanical fault or hijacker interference.

Hello,

As an forensics professional, you are aware that magnetic force microscopy has never been used to recover data off once-overwritten magnetic media. I assume you are also aware of the 2006 NIST Special Publication which stated that using magnetic force microscopy to recover data from magnetic media of any considerable density is impossible. Since you would know all this, I wonder why you would make such a statement.

It is also irrelevant since the CVR/FDR would not be recording to magnetic tape on the accident aircraft.

No, once again, there is no circuit breaker for the CVR nor for the FDR in the cockpit on the 777.

And no, there is Emergency Descent mode in the FMS.

Chris McLoughlin of Inmarsat was just on The Kelly File. When she pressed him, he stated that the plane took the southern route. This was based on their comparisons of pings from other Malaysian aircraft that took the northern route.

http://foxnewsinsider.com/2014/03/20...-370s-location

Could the membership explain something to me please?

As I understand it, the a/c had reached 35K or so after departure, and then abruptly turned and descended to 12K over Malaysia on its way south. It eventually appears to have crashed at, or just beyond, the predicted fuel exhaustion radius.

Would that fuel exhaustion radius be the range at 12K, or for a B777 at a "normal" cruise altitude (i.e. 30-40K)? I imagine the radius at 12K is considerably shorter.

If it's the higher altitude, then the question in my mind is how/why did it regain altitude? If it could only be by commanded intervention, then I'm at a loss as to why it continued in a straight line.

Conversely, if it had all gone wrong an hour or so after departure, and they had headed home or to an alternate airfield, at 12K, but just not made it, why would the aircraft ascend (if it did) to reach the range that it appears to have.

Or is the range to where the search is currently centered "reasonable" at 12K?

@syseng68k
 

It's actually much easier to recover data from over-written digital media. FBI software can recover data from digital media that has been over-written multiple times, or reformatted repeatedly.

If in fact the airplane did get down to 12K over Malyasia, I find it disturbing that NO phone data was found. Not one passengers phone was left on or if a rapid decent no one tried to call home or anyone? Has there been any attempt to pull passengers phone records for the time frame??
As a commuter I see all the time peoples phones on, and not in airplane mode....

Roadster280

There is considerable doubt about the reported height of the aircraft as determined by radar. The INMARSAT data indicates that the aircraft flew at constant altitude and speed in order to reach the area that is now being searched for debris.

Radar tracking of primary returns can be very inaccurate unless a target is being deliberately targetted and tracked. The track and height of MH370 seems to have been derived from sweep recordings of the radar examined after the event. The aircraft was initially flying along civilian airways and not towards any military installations when it turned off its planned flight path. Since the aircraft was assumed to be a civil flight and did not represent a threat, it was not tracked. The estimates of the height and possible altitude changes were all calculated (or estimated) after it was announced that the aircraft had disappeared.

Clearly the military will not want to reveal the capabilities or shortcomings of their radar systems or alert status, so the radar data and height changes reported should be regarded as being possibly inaccurate or not having occured at all.

Ok, that makes sense. If the descent to 12K and then climb to a normal cruise altitude potentially didn't take place, then that answers my question. Thanks!

Pedanticism. The only things "found" straight away were small floating bits and the fin. The main wreckage, which included the main tail and fuselage sections and the recorders at the bottom of the ocean, was not found until almost 2 years after the prang.

Mobile Phone
 

A few comments on this thread about the lack of mobile phone use

4 years ago I flew from LHR via BKK to SYD. On departure I put the phone in the overhead bin. 23hrs later on arriving at SYD I went to turn it on only to find I'd not actually turned it off. The only messages were welcoming me to Bangkok and Sydney which surprised me given that we'd tracked over most of Europe.

Descent to 12000ft ... Red herring!
 

I understand the Inmarsat investigation has confirmed there was no descent below 30000ft.

It is exceptionally unlikely they followed the initial descent and then re climbed back to 30k.

They will find this aircraft. They have to. The insurance industry will finance a lot of it to try and ensure there isn't a repeat. Just like AF447.