777 Hits Weather Balloon in Cruise
 

I suppose it was inevitable.

N775AN, a Boeing 777-200 aircraft operated by American Airlines, was conducting flight AAL139
from London/Heathrow International, United Kingdom (EGLL) to Los Angeles International, USA
(KLAX) with 12 crew members and 273 passengers on board. During cruise flight at FL380
overhead Moose Jaw (CYMJ) SK, the flight crew reported a collision with what is believed to be a
weather balloon. The flight continued to destination and landed without further incident.
The operator’s maintenance conducted a visual external inspection of the aircraft, and no damage
was found. The aircraft was returned to service.

​​​​​​​Rather you mean "I suppose it was uneventful"?

Since nothing happened...

Or more likely it was exactly as meant - that it was inevitable a commercial airliner would collide with a weather balloon sometime.

No……I mean that it was inevitable. Fortunately, no damage this time.

Can I ask what would be the effects of ingesting a weather balloon into one of the engines? Aerodynamically plausible? Is it a designed-for occurrence?

Shouldn't the unpowered aircraft have right of way?

Chance as well as consequence of collision is very limited, so it is deemed to be an acceptable risk. The measurement package is more an issue than the balloon itself.

To be visible, it would need to have a transponder which would add a lot of weight. Alternatively, every aircraft would have to be able to receive and interpret the data the probe is transmitting.

Weather balloons already have a transmitter sending a signal every second or so. The US versions send GPS coordinates, pressure, temperature, and humidity. That is more than enough to avoid hitting them. The question is whether it is worth avoiding hitting them. It appears to be less than $100 (less the $15,000 to $50,000 fee for adding to each airplane) or a ground based transmitter could add it as an ADSB target transmission and make them visible to any ADSB-IN system in the related area.

The packages seem to vary between 109 and 500 grams, if you see the balloon the package is hanging some 60 metres lower. td might like to comment on an engine devouring a 500 gram package.


https://cimg2.ibsrv.net/gimg/pprune....4f06433b66.png

… flight crew reported a collision with what is believed to be a weather balloon …

No damage found, no evidence, no inflight effect on controls or engines.
Visual, or just a belief; who looks out during the cruise - 500 kts closure.
Was it a balloon?

:= More like how many of them Wx balloons (Or else) Went very close and never got noticed.

I used to work on a weather research project, where they were sending balloons up from the airfield twice a day. We had discussions with them about the risk of launching them when there were aircraft in the circuit. They gave us the radiosonde to hold. It was very, very light and encased in a polystyrene 'outer'. That removed all concerns about any collision damage risk. So much so that if we were returning to the circuit as they were releasing one, we would try to 'run into it'! They were never concerned about us doing this and when we said 'surely you don't want us to damage all the work you've put into preparing it for launch' they said 'you'll never hit it' ... and we never did!! (Their initial rate of climb is huge!!) So, if we couldn't hit them deliberately, the chance of an accidental collision should be extremely, extremely low. And, in such an extremely rare likelihood, very much unlikely to cause any damage.

There's little point in worrying about hitting something that's inevitable. :O

Although it depends on how 'dense' the half kilo package is, unless it is encased in something like a steel box, I doubt it would be meaningfully worse than hitting a couple kilo bird at 250 knots (which is currently designed and tested for). Might require some smoothing of a few fan blades afterwards.
Given the small odds of actually hitting a weather balloon, hitting it just right to ingest the instrument package in the engine would be right up there with being hit by a meteor in-flight...

As usual, a very sound post from tdtracer :ok:
Case closed :)

The weather balloon is entering ADSB mandatory airspace, and doesn't have ADSB out. That seems incongruous. Would be a cost to add, but then it is not needing to be particularly complex to give a useable tracking for the crews.

An SR-71 crew in the cruise saw a met balloon sail past and seemed to express gratitude that it was a miss and not a hit, 500 grams at Mach 3.2 gives a deal of kinetic energy.

Does the radiosonde return to earth when the balloon breaks? Is it then recovered (that sounds costly and hard work)

Can the radiosonde cause damage/injury when it falls back to earth?

thanks

Please look at the image in the post above, #9. The balloon carries a parachute for the payload. When the balloon bursts, the remaining equipment, including the radiosonde, rides the 'chute to earth.

As the sonde transmits position data as a course of it's normal operations, retrievable ones are likely found fairly easily.

Last April, over northern Michigan inbound to ORD we passed one pretty close. The F/O saw it first, passed off our left really close, hard to tell. My guess would be less than 100m. There would have been little time for any manuverings. Never saw one of those from the air before. 34-36.000´