Malaysian 777 missing in action

[John H Watson]

Still a needle in a haystack.

They are now saying that the aircraft was travelling faster than first thought, so may have run out of fuel earlier, putting the aircraft further north, closer to Australia.

The debris spotted may not guarantee that the aircraft is in the original search areas.

[Shiv Mathur]

How much difference would that make?  Okay, it ran out of fuel earlier, but it was going faster in that shorter time.  

Well, I'm sure they've taken all that into account.

[Jeroen Hoppenbrouwers]

Wind drift, for example.

[Hardy Heinlin]

How much difference would that make?  Okay, it ran out of fuel earlier, but it was going faster in that shorter time.  

The aerodynamic drag rises with airspeed, and this ratio is not linear. The drag rises exponentially.

Say, you have 100 tons of fuel in the tanks, and you want to fly at 9999 kt. Your tank would be empty in 3 seconds. And the distance flown would be 3 miles. This is because the drag at that speed would be nearly infinitely high.

If you would fly at 9 kt, you could fly around the earth with those 100 tons. This is because the drag at that speed would be nearly infinitely low.

That's why we use a cost index in the FMC. If you want to fly faster, you will not only arrive earlier, but your fuel costs will rise as well -- exponentially. Think of the Concorde: Twice as fast, but the fuel burn ... what ... 4 or 6 times higher, compared to subsonic aircraft.


Cheers,

|-|ardy


P.S.: Yes, and wind drift, for example. If you need 3 minutes for the flight from A to B, your crosswind will not have a big effect. If you need 3 days for that same distance, that same crosswind would move you 999 miles sideways, provided you maintain the same heading. And if you would compensate the crosswind by turning your heading into the wind, you will maintain the track from A to B, but you will also need additional fuel because your will have to fly more air miles than ground miles. -- If the crosswind is as high as your TAS, you would have to turn your heading by 90°, into the wind, and you will never arrive at B because your ground speed would be zero. As you can see this adds another non-linear factor.

[Shiv Mathur]

Oh, ... I had no idea the drag would be so severe.  

Thanks for the explanations.

Shiv

[IefCooreman]

There is only a very small "speed" region where drag remains relatively "flat", that's the region between max range (minimum drag) and long range (99% of ME range, but offset by speed increase). So anything above long range speed will increase fuel burn. To give you an idea of how fuel costs have risen: we fly a cost index that ends up in a speed below long range. Our "playing field" is 0.82 to 0.84 (777). Increase to 0.85 and you will quickly burn 1000kg more on a 8hr flight.

If you would fly at 9 kt, you could fly around the earth with those 100 tons. This is because the drag at that speed would be nearly infinitely low.

Considering the fact that the aircraft can still fly at the same angle of attack you mean then :-). Because lower speeds require higher AOA's, and drag will increase in almost the same way.

Recently we were put in a strange situation: departure slot, and arrival (parking) slot, but they weren't very realistic. For a flight of 8 hours we now had to do 8hr30. Easier said than done! We reduced speed in cruise, but once you go below 0.81 you will notice the fuel on arrival starts to decrease again because the whole flight you'll be flying at a higher AOA, hence increasing your fuel flow (despite the lower speed). Some call this "flying the backside of the power curve", which lacks "speed stability" (lower speed creates higher drag, leading to even lower speeds and higher drag and so one...). Anyway, we made it with a very long rollout and a very long and slow taxi. Much more efficient than playing with speeds in flight :-).

[Hardy Heinlin]

Yes, bad example, these 9 knots, doesn't work with aircraft actually :-) (I was just considering the other half of the power curve.)

Anyway, we made it with a very long rollout and a very long and slow taxi. Much more efficient than playing with speeds in flight :-).

Or you could have spent the free time in a hold and use the time for inflight systems training ... or other airwork :-)


Cheers,

|-|ardy

[IefCooreman]

Lol, too dangerous... Even when I asked for the long rollout, they replied "state reason, do you need assistance?". Anything strange and they've got their hands on that big red knob. it's either normal or you get the full show, there is no in between! :-)

[John Golin]

Interesting stuff Ief, thanks!

[74pilot]

It is unlikely that there is independent Inmarsat on an engine. The cost is prohibitive and the weight impossible, let alone the bathtub-sized antenna fairing. However it is not impossible to put up Iridium. Even this I doubt, it is against common practice. Everything is relayed through one CMU that selects the cheapest radio (data plan is everything!). The rumours have it that the system worked but that Malaysian didn't have a monthly plan so they did not receive their data (cost versus utility decision). But the machine sends it. It is just the comms company not relaying.


Hoppie

I have a small hand held two-way messenger/GPS/Emergency unit (inReach SE). It's about the size of a mobile phone, and the battery lasts 100 hours if sending out position updates every 10 minutes. Price is 300 USD in retail, compare that to the price of a 777 engine.

This doesn't warrant whether or not the engine has its own transmitter - I'm just saying, it needn't take up a lot of space, and I see no reason why the engines couldn't have one.

I wish it would be disclosed properly and as fact - do the engines transmit directly to Inmarsat, or does it go through the ships onboard ACARS?

[John Golin]

It would be via the Standard onboard systems...

(..off to Google...)

Yep.

http://www.rolls-royce.com/about/technology/systems_tech/monitoring_systems.jsp

See the section 'Transfer'

[Jeroen Hoppenbrouwers]

An emergency transmitter, yes, but not a routine data relay for remote telemetry and maintenance. I'm not saying it cannot be done, but there is no commercial ground for such equipment yet. A regulatory mandate to equip (parts of) transport aircraft with permanent, independently powered, non-connected and robust tracking devices may change this. On the other hand, there is a reason to delay tracking data available to the public 5 minutes or more. Any tracking device will in some minds turn an aircraft into a "shoot me, shoot me" duck.

Complex, as usual. And it does not prevent any accident...


Jeroen

[Phil Bunch]

Additionally, the accident rate per scheduled flight from commercial airliner crashes, especially those involving "falling out of the sky" or "disappearing", is so incredibly low, I don't personally believe it makes any sense to make airliners any safer. Only if some sort of trend develops involving hijacking airliners and disappearing them to Somalia, etc, would it make sense to track them in real time.   Basically, it's almost literally impossible to die while involved in flying somewhere on an airliner.

Most of the time I personally believe the primary reason we've made airliners so incredibly safe is that most of us have a deep fear of dying by falling out of the sky, especially if we are exploded into small pieces along the way down.  

This is perhaps another way of agreeing with Jeroen H's comments pointing out that it would be a significant cost item to add such capabilities and the associated infrastructure to the airline's infrastructure and the needed components to the airliner itself.   I've always been deeply astonished when I learn how costly even the simplest FAA certified airplane parts are, and how expensive it is to keep even a simple component tested and maintained.

Also there is the additional issue of whether or not spending safety-related money on an airliner tracker is more effective than spending more money on (for example) a better deicing system for airspeed instrumentation.  Or, maybe we'd do better if we insisted on higher standards for staff training in the less developed countries that seem to be doing more and more airliner maintenance these days.  

Unfortunately (?), for any change we propose, the accident rate is so low for airliners we'd probably have to live 1000 years to actually observe fatality rates and verify that we've actually helped airline safety.  In other words, it seems to me that we can't verify the effectiveness of any changes by observing an actual reduction in crash probabilities.

Maybe airliners are already much too safe?  To me, this is a philosophically difficult issue, one that I can't personally reconcile with wanting the things to be perfect each and every time I board for a flight.

[Jeroen Hoppenbrouwers]

I'm currently in the middle of another discussion that touches upon the same kind of topic.

There's an FAA mandate that all new equipment for ATS datalink must record the CPDLC and other ATC-releated data messages to the CVR. This is easy.

Older equipment does not need to comply if it was certified and installed before about 2010. If anything major is changed or added to the radios, though, the installation must be made compliant with the data recording mandate.

So if you want to upgrade your D-VHF radios, or install an additional SATCOM, or even remove a SATCOM, you also need to upgrade your CMU, your CVR, and a lot of wiring. Easily add $100k to your upgrade bill. And for what? To have data recorder capability so people can play back your messages after the smoke clears up, while all those messages have been logged elsewhere triple-redundant as well. The irony is that installing a SATCOM has the capability to make your flight safer, but installing a recorder won't do anything for you (maybe for others after you). Plenty of companies don't upgrade or retrofit SATCOM because of this recording mandate, and it leads to hot debates here and there.

Safety isn't straightforward.

Data link isn't, either.


Hoppie

[farrokh747]

For the engineers :

What is the effect on a system, if the LRU itself is removed form the deck? for instance, what happens if the xpdr head itself is pulled out and disconnected? simple enough to do....  

does the system shut down since now a component is missing form the circuit..? Or say the door lock panel....  does it retain it's last settings?

fc

Also, search areas for MAS are now in hi rez on google earth....

[Jeroen Hoppenbrouwers]

Typical behaviour on a failing panel is "fail safe", the system tries to maintain its last-known setting.

[Jeroen Hoppenbrouwers]

CNN Español raided our lab for a FDR item. Luckily they overlooked the large SATCOM rack right behind them. It would have costed me a day...

http://www.cnn.com/video/data/2.0/video/spanish/2014/04/07/hauser-black-box.cnn.html


Hoppie

[Jeroen Hoppenbrouwers]

Official first report is out.

www.skybrary.aero/index.php/B772_en_route_suspected_location_southern_Indian_Ocean,_2014

[Will]

...and the word "CONFIDENTIAL" is stamped on every page. Gotta love the Internet.

[farrokh747]

http://www.huffingtonpost.co.uk/2015/07/29/mh370-experts-analyse-wreckage-plane-wing-found-reunion-island_n_7896548.html?1438188738

not sure if this a hoax, but popped in my feed today....