Yet another aviation thread.

Quote: Pacomartin

If JFK-LHR is 3,451 miles and the Concorde could reach a top speed of 1350 miles per hour, and the trip took 3.5 hours (average roughly 1000 mph), it seems that some reasonable percentage of the trip must have been subsonic.I have never seen a detailed flight plan.

I didn't find one handy, but it stands to reason that building up speed takes time. Planes climb steeply for a few thousand feet, then more gradually until cruising altitude. At the same time they build up speed. I don't know how long it takes an A320 to reach a cruising speed of 800-900 kph, but it's likely not done before reaching 20,000 ft. at least. Also, cruising altitude is where the most efficient engine operation is attained (with a rather generous band for ordinary jets), so it may take that long. Concorde had to climb higher, too, around 60,000 ft. if memory serves.

Speed just isn't everything, now that I come to think about it. I still want to see SSTs proliferate and be made as economical as current jets, but I'm beginning to doubt where and when that will be possible.

Consider this analogy. Suppose you have a self-driving car that's absolutely reliable. That is, it will get you from A to B without your supervision being needed. So, if you have to travel, say, 600 miles for a meeting next day, wouldn't it make more sense to leave at 9-10 pm and sleep in your car overnight while you travel, rather than to wake up early to catch a morning flight? The latter is faster, but the former is far more comfortable. Especially if you can set up your car with the equivalent of bedding for the trip, which isn't at all impossible nor expensive.

At the same time, short flights won't be a good fit for an SST. Say MEX-MTY, where you could perhaps reach Mach1.5 for a few minutes, and reduce the trip by 15-20 minutes or so. But MEX-LAs, currently at 3:30-3:45 hours, would be worth doing if you could reduce the trip to, say, 2:00 or less.

I once flew Tampa Bay to Orlando (the flight was MEX-Tampa-MCO). The cities are very close. Pretty much we took off, climbed, cruised for maybe 5 minutes, then began to descend. It was the shortest flight I ever experienced. Imagine an SST there, it would be exactly the same.

When Concorde flew from JFK to MEX, it swung out to see and went supersonic until it had to cross land again. That was faster than a direct route. How much faster, I've no idea. The regular flight is 5-5:30 hours long.

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You may be correct that Boom is overselling this early in the game. If the final product comes in at Mach 1.8 it should still have a market.

If they've not oversold on price, too. But I keep saying this is first generations stuff.

Quote: Nareed

I didn't find one handy, but it stands to reason that building up speed takes time. Planes climb steeply for a few thousand feet, then more gradually until cruising altitude. At the same time they build up speed.

The Shanghai Maglev Train (SMT) began construction in March 1, 2001, and public commercial service commenced on 1 January 2004. The top operational commercial speed of this train is 431 km/h but the length is only 30.5 km. I always wondered who would build such a train as it could barely reach top speed before slowing down to come to the station, but then I read a statement from the CEO of the German company who built the train. He said it was possibly the only billion dollar demo project in the world, because at the time they were hoping that the publicity would lead to contracts for some critical intercity routes in China (possibly the Beijing to Shanghai train).

If you understand the SMT as a "demo project" than a lot of stuff makes more sense. When a group from San Diego went to Shanghai to look at the train because they were considering a 150-200 km train to a new airport in the desert I realized it was just boondoggle.

Information on the crash in Colombia has been flowing very quickly. The aviation blogs are singling out fuel starvation already.

It's a big possibility. There was no fire, which is highly unusual in such an impact. But if there's little fuel left, the odds of fire are small.

The two indisputable facts I've seen are 1) the flight crew declared a fuel-related emergency (or requested priority due to low fuel), and 2) the crew reported electrical problems before vanishing off the radar.

The two fit. If you lose all engines because you're out of fuel, you also lose electrical power. And that qualifies as an electrical problem.

The question remains whether the crew failed to load enough fuel on board (for whatever reason), or whether there was a leak. Reports say the range of the odd plane was about the length of the flight. But range is dependent on a host of conditions. For instance, a tail-wind can increase range by a lot, and headwinds can reduce it as much. Other things such as takeoff weight, temperature, and altitude also are factors.

The plane's captain ultimately decides how much fuel goes onboard. And this amount changes in every flight depending on conditions, flight plan, weather, weight, winds, etc.

Granted, when fuel is an issue, most of the time the error lies in not taking in enough fuel before takeoff. But not always.

I could speculate about glide and what electrical problems means, but I won't. I can too easily construct scenarios which are likely not to fit in with the full facts.

Quote: Nareed

The two indisputable facts I've seen are 1) the flight crew declared a fuel-related emergency (or requested priority due to low fuel), and 2) the crew reported electrical problems before vanishing off the radar.

It should be noted that the jet was in a holding pattern for 15 minutes before the crash.


As the flight was 2800 miles long, I would expect close to a 5-6 hour flight. You would think that having extra fuel for a 15 minute holding pattern would be routine.

This plane, is also operated by the Queen's flight, the branch of the British military that takes care of VIP and royal flights. It is the 13th hull loss accident of a plane of which only 387 were produced.

Quote: Pacomartin

It should be noted that the jet was in a holding pattern for 15 minutes before the crash.

I found that odd, too.

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As the flight was 2800 miles long, I would expect close to a 5-6 hour flight. You would think that having extra fuel for a 15 minute holding pattern would be routine.

If it can hold it.

The plane, an Avro regional jet which has been mentioned here before, seems an odd choice for such a flight. Marginal operators sometimes take huge risks with fuel and maintenance.

I have mentioned before that is my favorite plane. A small overwing four engine jet that I used to fly on as a commuter flight into Chicago. I am shocked to see that it has a range of 2800 miles. I would have expected it to be under 2000 miles.

Too much attention to the soccer players?

In the US 'low fuel' is meaningless. 'Minimum Fuel' is the mandatory phrase for priority but not emergency scheduling. Latin pilots don't always like to admit their errors publicly but , well, the analogy that seems best is admitting your predicament and being allowed to cut to the head of the line for the porcelain at the baseball stadium.

Quote: DRich

I have mentioned before that is my favorite plane. A small overwing four engine jet that I used to fly on as a commuter flight into Chicago. I am shocked to see that it has a range of 2800 miles. I would have expected it to be under 2000 miles.

It appears that I made a mistake. The distance from their home town airport, Chapeco Airport, is almost 2800 miles, but they did take off from an airport in Bolivia which was only 1839 miles from Medellin. They may have made an intermediate stop to refuel.
VVI MDE :1,839 mi

Wikipedia lists the Range as 1808 mi with standard fuel tanks. If so than a flight of 1839 miles with a 15 minute delay might have made them run out of fuel.

Just before LaMia Flight 2933 crashed into a hillside a crew member onboard told air traffic controllers, "The plane is in total electric failure and without fuel," according to two sources familiar with the investigation who heard audio recordings.

Quote: Pacomartin

Wikipedia lists the Range as 1808 mi with standard fuel tanks. If so than a flight of 1839 miles with a 15 minute delay might have made them run out of fuel.

I've been hearing lots of pilots say the range estimates are so dependent on so many factors, that they're largely meaningless. Patrick Smith goes so far as to imply you need to judge all factors particular to this flight to determine whether the crew played it too close.

However, all indications seem to be they were.

Quote:

Just before LaMia Flight 2933 crashed into a hillside a crew member onboard told air traffic controllers, "The plane is in total electric failure and without fuel," according to two sources familiar with the investigation who heard audio recordings.

If you lose fuel you lose the engines and electrical power. Jets have an emergency wind-powered generator that's deployed in such situations, though. No idea whether this plane didn't have one, the crew didn't deploy it, it malfunctioned or what happened.

Quote: Nareed

I've been hearing lots of pilots say the range estimates are so dependent on so many factors, that they're largely meaningless.

I generally regard them as upper bounds since they are selling points, and they tend to assume no real world problems. Now this plane was designed to have up to 112 passengers in it's commercial version, so they may have been counting on the reduced load of only 68 passengers. There are also up to 3 different auxiliary tanks which are possible. It is not clear what the exact configuration of this plane was.

Note that 1839 statute miles = 1598 nautical miles. So it seems likely there was at least one auxiliary tank (if not all three).

The green line is standard
The blue line is one auxiliary tank
The purple (olive) line is two auxiliary tanks
The red line assumed three auxiliary tanks


The pilots began their descent to Medellin at around 21:30L. It was dark at the time. The winds were calm. Light rain was falling at the airport. The approach was flown without further abnormalties. Minutes before there was a priority flight supposed to land ahead of them. VivaColombia flight VVC8170 from Bogota to San Andres reported their diversion to Medellin due to a suspected fuel leak. This traffic, an Airbus A320 was turning to final approach when the RJ85 was instructed to enter a holding to give way to preceeding traffic.

At 21:43L LMI2933 accepted the instruction and began to fly a holding pattern at 21.000 ft about 17 miles southeast of their destination airport

Whilst in the hold, LMI2933 continued the descent and the pilots indicated some kind of electrical problems. A minute later the pilots requested priority handling indicating fuel issues to Air Traffic Control (ATC).

The occurrence report was sent at 22:00L, half an hour after their initial descent. So the total delay time does appear to be more than 15 minutes.