ReLAX From United States of America, joined Feb 2005, 26 posts, RR: 0 Posted (9 years 3 months 1 week 7 hours ago) and read 18189 times:
I was on EK 003 yesterday evening. When we were on approach to London, just having passed Canary Wharf, there was a distinct thump and the 777 banked right. I didn't think much of it - perhaps just rogue bit of turbulence. 30 seconds later, the captain came over the PA and announced that we had just collided with a meteoroligical balloon, but all was well.
Questions: 1) why would there be meteoroligical instruments flying over central London, and more importantly, in the path of Heathrow traffic and 2) what sort of damage could such an instrument do to the aircraft?
Zeke From Hong Kong, joined Dec 2006, 10111 posts, RR: 76
Reply 3, posted (9 years 3 months 1 week 7 hours ago) and read 18106 times:
Those balloons are sent airborne all over the world, to collect atmospheric data which is very important for the meteorological models and computerised flight planning systems that are in use. The actual winds will also influence the actual North Atlantic tracks for that are used for a particular day.
The most damage it could do would be like hitting a reasonable sized bird. Had something similar happen to me near HKG.
Seen NOTAMS for these to be released around, and enroute to some fairly large airports sometimes on a hourly basis.
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ReLAX From United States of America, joined Feb 2005, 26 posts, RR: 0
Reply 7, posted (9 years 3 months 1 week 5 hours ago) and read 17875 times:
We must have been at about 3,000 - 4,000ft. And no, there was no go around (guess all systems reporting normal?). The approached proceeded as normal - even with the overhead projector showing the forward camera.
I was shocked by the captain even announcing the event. All of us in business class looked at each other as if to say "does this mean an emergency landing?"
Corey07850 From United States of America, joined Feb 2004, 2530 posts, RR: 4
Reply 10, posted (9 years 3 months 1 week 4 hours ago) and read 17633 times:
Quoting ReLAX (Thread starter): 1) why would there be meteoroligical instruments flying over central London, and more importantly, in the path of Heathrow traffic
I'm sure it wasn't intentional... The balloon could have been released many miles away but the winds have carried it across your path. Since you estimate you were at 3 or 4,000ft, so it's not like you were on final approach... I doubt any balloons would be intentionaly released within a couple miles of the airport.
Quoting ReLAX (Thread starter): 2) what sort of damage could such an instrument do to the aircraft?
I wouldn't think anything that serious, however there are things it can do. Attached to the balloon is the actual instrumentation to make the recordings and I'm sure this isn't exactly light. It could possibly crack a windscreen or dent the leading edge of a wing or something. While not exactly life threatening, it could down the plane or maintenance and cost some $$$
I would think the worst case scenario is the balloon covering a pitot tube or maybe knocking a radio antenna off. However since large aircraft have multiple of each, it's still not that big of a deal.
A346Dude From Canada, joined Nov 2004, 1341 posts, RR: 7
Reply 11, posted (9 years 3 months 1 week 4 hours ago) and read 17574 times:
Quoting Corey07850 (Reply 10): Attached to the balloon is the actual instrumentation to make the recordings and I'm sure this isn't exactly light.
IIRC, it is actually fairly light. When the balloon reaches an altitude where the pressure differential is so great that it bursts, the instrumentation falls back to Earth. It must be light enough so as to do no damage if it hits an object on the ground.
You know the gear is up and locked when it takes full throttle to taxi to the terminal.
Packman From United Kingdom, joined Mar 2005, 92 posts, RR: 0
Reply 12, posted (9 years 3 months 1 week 4 hours ago) and read 17551 times:
I was at Heathrow early yesterday afternoon taking a few photos when a bunch of helium balloons passed over runway 09R between terminal 4 and Hatton Cross at about 1000 feet. Fortunately they crossed the runway between departing aircraft but I don't know whether they were spotted by the tower personnel.
Corey07850 From United States of America, joined Feb 2004, 2530 posts, RR: 4
Reply 13, posted (9 years 3 months 1 week 4 hours ago) and read 17538 times:
Quoting A346Dude (Reply 11): IIRC, it is actually fairly light. When the balloon reaches an altitude where the pressure differential is so great that it bursts, the instrumentation falls back to Earth. It must be light enough so as to do no damage if it hits an object on the ground.
You're right, I did some research and found that radiosondes typically weigh only about 250 grams
LXLucien From Switzerland, joined Mar 2005, 327 posts, RR: 4
Reply 18, posted (9 years 3 months 1 week 2 hours ago) and read 16907 times:
Some sort of balloon don't cause damage at the engine...
even a small bird you don't even realise it... maybe a little bit of turbulence at the engine and a soft smell of chicken inside the cabin (that's really no joke !)
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BO__einG From Canada, joined Apr 2000, 2771 posts, RR: 17
Reply 19, posted (9 years 3 months 1 week 2 hours ago) and read 16815 times:
They also shoot chunks of ice into engines as well during testing.
Also lots and lots of water for to simulate a heavy rainfall or monsoon.
For the chickens, well despite being all frozen once it is inside the engine and takes on the superheated gases it will litteraly spray out blood from the rear end in the area around a thousand degrees.
You dont want to be sprayed by superhot chicken blood.
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Boysteve From United Kingdom, joined Apr 2004, 964 posts, RR: 0
Reply 21, posted (9 years 3 months 1 week 1 hour ago) and read 16325 times:
Quoting Noah008 (Reply 17): they throw frozen chickens? thats crazy what else do they throw at an engine for testing? and doese anyhting come oiut the back side?
This reminds of a funny but true story. It's not directly related to commercial airlines but I feel it is worth telling none the less.
When British Rail was testing the High Speed Train in the early to mid 1970's they wanted to ensure that a bird strike could not break the windshield and thus injure the driver. They knew that NASA tested the windshields of its space vehicles by firing frozen chickens at them at very high speeds so decided to do the same. Every-time they carried out the test the windshield smashed beyond recognition and British Rail staffed could not work out why their test was failing. They made a phone call to NASA to explain their findings and to determine why the tests were giving different results. The answer that came back from NASA was loud and clear; "We thaw them out first".
Geo772 From United Kingdom, joined Jul 2004, 519 posts, RR: 0
Reply 22, posted (9 years 3 months 1 week 1 hour ago) and read 16160 times:
Remembering back to my days at school I went on a trip to a site that launched weather ballons. These were about 8ft high on the ground but only about a foot to eighteen inches across at the widest point. I forget how big they got to at altitude but it is pretty enormous.
Contrary to popular belief fresh chickens are used on engine bird stike tests, for the simple reason that in nature a frozen bird cannot fly into an airplane engine.
The Ice tests are done to check that the engine can still run with cowl icing, a most undesirable occurance.
It is also quite rare for an engine birdstrike to result in the bird going down the hot core of the engine, normally they end up being flung down the cold stream duct and it is usually a horrble mess.
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