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Jet goes down on its way to Medellin, Colombia

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Jet goes down on its way to Medellin, Colombia

Old 12th Dec 2016, 22:10
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Originally Posted by Airbubba
It looks like FR24 had six receivers near MDE that could provide multilateration location data on playback. Some of the other flights depicted on the playback animation seem to be MLAT only with occasional position shifts due to terrain and receiver geometry.

I think FR24 will default to displaying ADS-B data when it's available. I'm wondering if MLAT data for LMI2933 is available somewhere in the FR24 database for comparison to the transmitted ADS-B track.

Were the pilots of the RJ85 seeing a map display updated by radio navaids while the ADS-B was sending inertial only data?

Or, was the cockpit nav display also showing the wrong shifted position for some reason? The fact that the plane crashed so close to the VOR instead of the runway threshold makes me wonder.
It would not take too many MLAT measurement to rule out an 8 nm error in the FR24 reports, which I believe to represent raw IRS 1 position.

I dwelled a lot in the blog on how the GNS-X computes composite position for LNAV, and how this could be a factor (map shift?) in leading the flight crew to believe they were operating much closer to MDE than they may have been. But this is just a convenient explanation, I don't have anything to say that is what happened.

The descent captured to the last reported position (FR24) aligned (with a reasonable offset) to the final resting place, both in range and bearing.

The transponders are lost with EMERG AC/DC. As is EFIS. And DME. The crew would resort to LOC on the standby Attitude Indicator and VOR on the DBI, neither of which would reveal the displaced position since they were flying along a line (the VOR cross-over would be noted). They were above the G/S until after flameout.

If the FR24 data was wrong, that LMI2933 was operating much closer to the airport than recorded, than the final resting place does not add up assuming a controlled descent generally northbound. It would imply something like a 5,000 fpm descent rate which makes time aloft a question too (need to look into that from the transcript). Another option is a circling descent, but again that does not seem consistent with the pilot reports.

The glide ratio (flaps up or flaps down, gear ***DOWN***) is 1 nm per 1,000 feet (6:1). It is arguable what the descent rate would be for flaps down, assuming both are flown at best glide speed. They lost engines about 8,000 above the runway, which means they should have been able to glide some distance (8 nm?). I was assuming a V/S of about 2,500 fpm would yield about three minutes of flight at about 140 KTAS or about 7 nm.

Glide Ratio (Flaps Up, Gear up) is 2.5 nm per 1,000 feet.p (15:1).

The SSR data will resolve this point, and maybe the flight data recorder will offer some insights.

Last edited by lemme; 13th Dec 2016 at 07:50.
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Old 12th Dec 2016, 23:56
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Originally Posted by H Peacock
AerocatS2A, I'm not criticising your use of LRC data, but simply highlighting that, if you really do want to achieve maximum range, LRC is invariably not going to be the speed to fly at.
Ah yes, fair enough. In fact the LRC technique for the 146/RJ isn't even a traditional LRC, it is a single indicated airspeed (235 KIAS for the RJ85) that is used regardless of weight. At heavy weights it is slower than ideal and at light weights it is faster. Something else you can do if range is critical is to disengage the autothrottle and manually set the power.
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Old 13th Dec 2016, 06:35
  #883 (permalink)  
 
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Originally Posted by lemme
The glide ratio (flaps up gear up) is 1 nm per 1,000 feet.
Are you sure about that ?

That's about 6:1. The conventional wisdom is that a typical two-engined narrow-body (A320, say) can achieve about 17:1 clean.

Clearly a short, stubby, high-winged, 4-engined aircraft won't do as well, but is the difference really almost 3 times worse ?
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Old 13th Dec 2016, 07:40
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I read some place, forgot where, but it semed like someone who knew what he was talking about, or maybe it also was a link to some paper included, anyway, he claimed the glide ratio was about 13:1 in clean configuration. I think he said that the ratio with gear down was only like 6:1, but dont quote me on that last number.
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Old 13th Dec 2016, 07:52
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Originally Posted by DaveReidUK
Are you sure about that ?

That's about 6:1. The conventional wisdom is that a typical two-engined narrow-body (A320, say) can achieve about 17:1 clean.

Clearly a short, stubby, high-winged, 4-engined aircraft won't do as well, but is the difference really almost 3 times worse ?
Sorry, typo. I fixed it. I have two references in the blog. Flaps up Gear up clean is 15:1. Flaps up or down, gear down is 6:1.
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Old 13th Dec 2016, 12:53
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On the A320 the lowest drag with full flap and gear down is twice the best clean aircraft value. The RJ landing gear is quite short in comparison so the difference would not be quite so pronounced. 6:1 sounds a little low starting from 15:1
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Old 13th Dec 2016, 12:54
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Update 6 - impact and breakup sequence - background information published 12/12

... Rafael Henzel (43yr) journalist "No one told us to fasten our seat belts," he said. "Every time we asked when we'd arrive we were told '10 minutes'." "Then the lights and the engines went off. That scared us somewhat, but we weren't warned of anything. We didn't know what was going on," Henzel said. He recalled how people rushed back to their seats when the plane went dark. But he said that no-one had expected the plane to crash. Return home - The journalist described sitting in the penultimate row of the plane, between two other journalists.

Last edited by A0283; 13th Dec 2016 at 13:27.
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Old 13th Dec 2016, 16:47
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Avro clean will glide at 2.5nm per 1000' according to the manufacturer. that's about 15:1

They suggest staying clean until you have 1000'=track miles then configure and maintain 1000'per nm.

FCOM vol 3 Part 1 Ch10 Topic 8.5.
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Old 13th Dec 2016, 18:20
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In 2010, a City Jet RJ85 encountered a low fuel situation. If only LMI2933 had learned these lessons.

At 17 h 26 min 16, while the BAe146 was 1.8 NM from the runway threshold, the crew of the A319 not having taken off, the tower controller told them : “stop immediately, hold position, repeat, stop immediately, a BAe 46 on go-around“. Then he asked the crew of the BAe to make a go-around. The latter refused because they did not have enough fuel and requested that the A319 vacate the runway.
Note: At this time and according to the airline’s analysis, the quantity of fuel remaining was estimated at 1,400 kg. The nal reserve is de ned as 850 kg.
At 17 h 26 min 36, the controller ordered a go-around, which the crew performed.
At 17 h 26 min 58, the crew stated: “we are declaring a fuel emergency now we request priority vectors for landing“.
The tower controller contacted the approach controller by telephone. They decided to have the airplane climb to 6,000 ft on the extended runway centreline and to “make it as short as possible “. The tower controller asked the crew to climb to 6,000 ft and to change frequency.
At 17 h 28 min 23, the crew of the BAe 146 contacted approach control: “Mayday Mayday Mayday, City 108X, declaring fuel emergency, request priority landing“.
After ensuring that they had the runway in sight, the approach controller offered the crew of the BAe 146 a visual approach, which was accepted.
At 17 h 34, the crew landed.
On the ground, the quantity of fuel remaining was 1,220 kg.

The Captain stated that he declared an emergency because:
ˆ He did not know the number of aeroplanes on landing there were in front of him and considered that if there were 5 or 6 aeroplanes, his landing fuel would be below the minimum regulatory quantity;
ˆ He had a low-level fuel caution.
He stated that he did not apply the “low fuel quantity“ procedure as he had priority
to land and he was concentrating on the visual circuit and the landing procedures.
CONCLUSIONS
The incident was due to the late communication by the crew to the Air Traffic controller of their low fuel situation and their emergency situation. This led to the controller being unaware of the emergency situation.
The following elements contributed to the event:
The lack of an appropriate “minimum fuel“ procedure associated with the remaining flying time.
Notion of minimum fuel
The notion of minimum fuel defined by ICAO allows a crew to describe to the air traffic services a potentially critical situation during a diversion while avoiding the declaration of a distress or emergency situation.
This notion of minimum fuel is not defined in the European regulation.
In its report on the serious incident on 28 August 1999 at Paris Charles de Gaulle (95) to the Boeing 737-528 registered F-GJNF operated by Air France, the BEA had already recommended that the DGAC define the “Minimum fuel“ callout. In answer to this recommendation the DGAC considered that: “The minimum fuel callout is a source of confusion. This callout does not lead to any action by ATC, so the crew must then declare a distress situation as soon as the quantity of fuel planned for the landing is lower than the final reserve“.
In the light of this event, the BEA recommends that:
€the DGAC and EASA implement the “minimum fuel” message already defined by ICAO, with the associated procedures. [Recommendation FRAN‐2012‐026].

https://www.bea.aero/docspa/2010/ei-...w100617.en.pdf
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Old 13th Dec 2016, 19:20
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Ex ATC :

(1) ."2933: Requesting vectors for inbound leg ma'am

(2). 2933: We are with emergency fuel ma'am. We're established on final approach course. request immediate descent, LMI 2933

(3). Approach: LMI 2933 you can just turn right now to start your descent. You have traffic 1 mile and below
2933: Traffic in sight, no factor(?) and we request to join the localizer for once (?)

(4). LMI 2933: We have it on TCAS and just above. ma'am we're on final course

(5). LMI 2933 Ma'am LMI 2933 is with total failure, total electric and fuel
Approach: Runway is clear, LMI 2933 and fire services are rolled
2933: Copied, LMI 2933... vectors vectors ma'am vectors to the runway"

In 1 they request assistance for landing and yet in 2 above the crew appear to know their position.
At 3 they seem to be making a rather strange request.
At 4 once again it would seem they know their position, that they are aligned with the rwy.
At 5 they are calling for assistance to steer them towards the rwy.

Seems very confusing just reading it at my desk on the ground. I wonder what it must have sounded like to the controller.
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Old 13th Dec 2016, 19:39
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My best guess:
(1) vectors was for separation, they knew their own position, they were looking for clearance.
(3) i have no other info, but was it localizer for oh one, zero one, runway 01?
(4) this could be on course for intercept, or on extended localizer
(5) with EMERG power, navigation is down to loc deviation and direction bearing with VOR and no DME. The VOR signal seems accessible, but the loc may have been lost as they descended too low.
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Old 13th Dec 2016, 20:59
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Is it possible that the last request, though unstated, was a panicked cry for vectors Around the mountain?

Last edited by thcrozier; 14th Dec 2016 at 01:40.
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Old 13th Dec 2016, 21:06
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If they could see it, they could vector themselves around it.
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Old 13th Dec 2016, 21:12
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But they couldn't see it, they just knew it was there.
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Old 13th Dec 2016, 23:56
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It was dark, in support of thecrozier's point.
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Old 14th Dec 2016, 01:56
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Originally Posted by thcrozier
But they couldn't see it, they just knew it was there.
If they knew they were dropping below glidescope, does it follow that they knew they would hit the mountain without vectors?

The latest report from a surviving passenger is that no PA was made to the cabin, would the PA have been working after the lights went out? He also said people had been standing. This is corroborated by the surviving crew member who said that passengers were standing and shouting during "the situation".

If they were standing before the lights went out, as claimed by the passenger, had word filtered back from cockpit that they were in strife?


At what point did cockpit crew realise they were doomed and would the PA have been working at that point?

For 4 passengers this was a survivable accident even though they apparently were not prepared. How many more could have survived had they adopted a brace position?

Perhaps the fact that Erwin Tumiri, the flight engineer who is one of the two crew members who survived, had prepared himself for the crash, is an indication that more passengers could have survived if they had been warned?

There are no reports yet of cabin crew running down the aisles instructing passengers to brace.


Shortly after the crash, Tumiri, a flight engineer, reportedly told media outlets that he survived by curling up in the fetal position with a bag between his knees as the jet careened toward the mountainside.

“I put the bags in between my legs to form the fetal position that is recommended in accidents,” he told Fox Sports Argentina in Spanish. “During the situation, many stood up from their seats, and they started to shout.”

Last edited by mickjoebill; 14th Dec 2016 at 02:08.
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Old 14th Dec 2016, 03:26
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From FCOM Vol 1, similar RJ85, while on EMERG DC:
Passenger Address should be functional through audio channel A.
Cabin interphone is inop.
The right hand mic is inop.
Is there a portable cabin megaphone?
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Old 14th Dec 2016, 13:18
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I think it fair to say that the flight deck crew were behind the aircraft as soon as it went dark. That suggests to me that they lost enough SA to be unaware that they needed to warn their passengers ... but wouldn't the "fasten seat belts" sign have already been put on before they began descent, or did they forget to do that as well when the fuel/time problem cropped up due to the instructions to hold?
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Old 14th Dec 2016, 14:19
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That suggests to me that they lost enough SA
Didn't that happen even before take off?
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Old 14th Dec 2016, 22:51
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If there was no PA then presumably the fight engineer knew to brace because he heard the engines wind down or had he been looking at his watch? Wonder if he told others to brace?
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