Airlander 10 "breaks in two"
Discussion
saaby93 said:
Ayahuasca said:
back of an envelope maths:
Airlander 10 is 92m long and 26m high, so a side area of 2,392 square meters. (wiki)
Wind power at 50 metres altitude is 400 watts per square meter if the wind speed is 15 knots (google).
So wind energy hitting Airlander 10 (if stationery, and perpendicular to the wind direction) is 956,800 watts.
She has 4 × 4 litre V8 turbocharged diesel engines, 242 kW (325 hp) each, so a total of 968,000 watts.
So in a side wind like that she would need all her engines to be facing exactly sideways, at almost full power, just to avoid being blown away, and no spare power for forward flight.
What could possibly go wrong?
(awaits correction by more knowledgeable folk, possibly invoking basic errors in arithmetic or the behavior of lighter than air craft in wind, who might also mention that her profile is rounded, not flat, so some wind energy would be diverted around her, but still..)
Isnt the idea like with a hot air balloon you either generally go with the flow or change height to suit alternative wind directions. Airlander 10 is 92m long and 26m high, so a side area of 2,392 square meters. (wiki)
Wind power at 50 metres altitude is 400 watts per square meter if the wind speed is 15 knots (google).
So wind energy hitting Airlander 10 (if stationery, and perpendicular to the wind direction) is 956,800 watts.
She has 4 × 4 litre V8 turbocharged diesel engines, 242 kW (325 hp) each, so a total of 968,000 watts.
So in a side wind like that she would need all her engines to be facing exactly sideways, at almost full power, just to avoid being blown away, and no spare power for forward flight.
What could possibly go wrong?
(awaits correction by more knowledgeable folk, possibly invoking basic errors in arithmetic or the behavior of lighter than air craft in wind, who might also mention that her profile is rounded, not flat, so some wind energy would be diverted around her, but still..)
And check the weather forecast
thegreenhell said:
saaby93 said:
Ayahuasca said:
back of an envelope maths:
Airlander 10 is 92m long and 26m high, so a side area of 2,392 square meters. (wiki)
Wind power at 50 metres altitude is 400 watts per square meter if the wind speed is 15 knots (google).
So wind energy hitting Airlander 10 (if stationery, and perpendicular to the wind direction) is 956,800 watts.
She has 4 × 4 litre V8 turbocharged diesel engines, 242 kW (325 hp) each, so a total of 968,000 watts.
So in a side wind like that she would need all her engines to be facing exactly sideways, at almost full power, just to avoid being blown away, and no spare power for forward flight.
What could possibly go wrong?
(awaits correction by more knowledgeable folk, possibly invoking basic errors in arithmetic or the behavior of lighter than air craft in wind, who might also mention that her profile is rounded, not flat, so some wind energy would be diverted around her, but still..)
Isnt the idea like with a hot air balloon you either generally go with the flow or change height to suit alternative wind directions. Airlander 10 is 92m long and 26m high, so a side area of 2,392 square meters. (wiki)
Wind power at 50 metres altitude is 400 watts per square meter if the wind speed is 15 knots (google).
So wind energy hitting Airlander 10 (if stationery, and perpendicular to the wind direction) is 956,800 watts.
She has 4 × 4 litre V8 turbocharged diesel engines, 242 kW (325 hp) each, so a total of 968,000 watts.
So in a side wind like that she would need all her engines to be facing exactly sideways, at almost full power, just to avoid being blown away, and no spare power for forward flight.
What could possibly go wrong?
(awaits correction by more knowledgeable folk, possibly invoking basic errors in arithmetic or the behavior of lighter than air craft in wind, who might also mention that her profile is rounded, not flat, so some wind energy would be diverted around her, but still..)
And check the weather forecast
Still, I think the maths might work: assume the wind is from 90 degrees to direction of travel and the airship (with inline propellers) is angled 45 degrees to windward. The area exposed to the wind has reduced by half (because geometry) but the power to windward has reduced by half too (because vectors) so while it may just about maintain its overland track, its forward speed has reduced by 50%. All this assumes that the engine operate at full power all the time, and that the propellers are 100% efficient in turning engine power into motion, both of which are not practical.
Bottom line - airships have unfeasibly large areas exposed to wind (compared to a normal aircraft) compared to their power. And in the event of an engine failure they are completely at the mercy of the elements. I think.
“Bottom line - airships have unfeasibly large areas exposed to wind (compared to a normal aircraft) compared to their power. And in the event of an engine failure they are completely at the mercy of the elements. I think. ”
And a jet airliner is at the mercy of gravity if its engines fail.
And a jet airliner is at the mercy of gravity if its engines fail.
He has a point. Structurally, airships, even those built from modern materials, are very weak compared to their size. And they really are at the mercy of updrafts, downdrafts, sidewinds etc.
The available power to counteract sudden gusts is barely sufficient and, close to the ground, not sufficient at all - as demonstrated by the Airlander accident.
The available power to counteract sudden gusts is barely sufficient and, close to the ground, not sufficient at all - as demonstrated by the Airlander accident.
Eric Mc said:
The available power to counteract sudden gusts is barely sufficient and, close to the ground, not sufficient at all - as demonstrated by the Airlander accident.
The first one where the mooring lines were snagged on power lines or the last one where it wasn't anchored down properly? Tony1963 said:
And a jet airliner is at the mercy of gravity if its engines fail.
Not quite. An airliner is at the mercy of gravity if it's wings fail.The engine provide the power to over come drag, they do no lift the aircraft, that's what the wings do. You can have complete engine failure and still glide the aircraft. (Helicopters do rely on their engines to stay in the air of course)
Because modern planes are structurally extremely reliable it's not often an aircraft actually suffers a catastrophic structural failure in flight, there's the Comet crashes of course and the famous Aloha 243:
When you consider the tens of thousands of jet airliners that have been built since the first (the Comet 1), then the incidents of structural failure due to inherent weaknesses in the structure or unexpected phenomenon that caused the break up are quite rare. I would suggest that the percentage of jet airliners lost through structural failure is a very low percentage indeed.
When you look at the history of airships and airship accidents, you will see that most of the accidents were precipitated by some sort of structural failure.
When you look at the history of airships and airship accidents, you will see that most of the accidents were precipitated by some sort of structural failure.
Max_Torque said:
Not quite. An airliner is at the mercy of gravity if it's wings fail.
The engine provide the power to over come drag, they do no lift the aircraft, that's what the wings do. You can have complete engine failure and still glide the aircraft. (Helicopters do rely on their engines to stay in the air of course)
Funny! So what you're saying is that if an airliner's engines fail, it can stay up? It won't lose altitude? Lol, that's brilliant.The engine provide the power to over come drag, they do no lift the aircraft, that's what the wings do. You can have complete engine failure and still glide the aircraft. (Helicopters do rely on their engines to stay in the air of course)
And most helicopters, in the event of engine failure, can autorotate if the situation allows, thus landing in a controlled manner.
I think you need to reread theory of flight.
Edited by Tony1963 on Sunday 13th January 14:13
Aeroplanes do suffer structural break up from time to time - usually because they have endured loads beyond their capability caused by pilot mishandling or some other initial non structural failure, such as engine failure.
With airships, it's the structural failure that often precipitates the accident.
With airships, it's the structural failure that often precipitates the accident.
Tony1963 said:
Max_Torque said:
Not quite. An airliner is at the mercy of gravity if it's wings fail.
The engine provide the power to over come drag, they do no lift the aircraft, that's what the wings do. You can have complete engine failure and still glide the aircraft. (Helicopters do rely on their engines to stay in the air of course)
Funny! So what you're saying is that if an airliner's engines fail, it can stay up? It won't lose altitude? Lol, that's brilliant.The engine provide the power to over come drag, they do no lift the aircraft, that's what the wings do. You can have complete engine failure and still glide the aircraft. (Helicopters do rely on their engines to stay in the air of course)
And most helicopters, in the event of engine failure, can autorotate if the situation allows, thus landing in a controlled manner.
I think you need to reread theory of flight.
Loss of thrust in an airliner does not cause it to fall helplessly out of the sky (at the mercy of gravity) because it is able to convert height, into velocity and hence into lift with its wings. This is why air transport has a very different risk profile between fixed wing and rotary wing architectures. The critical point you seem to be ignoring is the effective L/D difference between an aricraft in a glide and an helicopter in autorotation. That vastly different value is what turns a helicopter engine failure into a critical "get it down right now" event, whereas a fixed wing aircraft, because of it's much higher L/D has significantly more time, and hence range within its glideslope. Of course it's still an emergency situation, but a large number of aircraft, particularly in GA, are landed with no, or minimal injuries each year after engine failure, precisely because they glide at a sensible slope:
You'll also note, as you have kindly quoted my original reply that at no point did i say "if an airliner's engines fail, it can stay up". I know we like arguing on PH, but please, lets not have an argument over your miss-reading of my post.
Here's two good examples of engine failures that didn't lead to a loss of control or life, and where the significant glideslope has given the pilot much more time to make a considered response:
PittsEngineStops
P51_engineOut_forcedlanding
Airliners glide better than you think. The Gimli Glider managed a glide ratio of about 12:1. So with an engine failure 8 miles high (OK, 7 really, but the lyrics wouldn't have scanned too well) a 96 mile glide would be possible. I think the record is held by a Lockheed U-2, but that's really a glider wing with a Starfighter fuselage bolted on to it.
ash73 said:
If we're serious about saving the environment this concept is the future, I wish it every success.
I too wish it all the best, I’m sure there’s a niche market there. But, the future? I can just see it, looking on Amazon for a car part. Wahoo, you find it, and it’s on Prime. Click buy, email comes through... six week delivery time, from America, weather dependent. 
) would love to see the return of large airships.Tony1963 said:
Lol, you're still avoiding the simple fact that weight is going to be bringing an airliner down. Dress it up as you want, the fact remains.
We could share videos of fixed and rotary winged aircraft landing without engine power til the cows come home, but still the fact will remain.
You can't make a safety case on equivalency between totally different machines, you have to make it against allowable levels of residual risk and actual accident scenarios.We could share videos of fixed and rotary winged aircraft landing without engine power til the cows come home, but still the fact will remain.
What makes heavier than air aircraft inherently safer than airships is that they have:
1: Substantially greater robustness
2: Substantially greater control authority
It is the control authority where the real difference lies. Even with a total loss of power an aircraft has control authority, a lighter than air craft does not, it will drift where the wind takes it.
Obviously hot air balloons fly with some degree of safety but they actually have much greater control authority in the vertical plane than airships and tend to make much shorter flight in benign weather.
The only argument in favour of an airship from a safety perspective is that in some scenarios your speed of operator action may be lower.
The principle issue for the lack of control authority in the airship is that it cannot handle significant air movements particularly when it is proximity to the ground. These scenarios happen far more frequently than propulsion failures which on commercial aircraft are vanishingly small.
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