Helium party balloons are said to go up about 10km before bursting — ie 32,000 foot altitude. Cruising level for many airliners. Surprising.

I imagine they could possibly get sucked into a jet engine approaching it at hundreds of km per hour. End result I have no idea. And would rather not be on the plane to find out! Possibly trivial as the rubber is light and would melt in short order. Or possibly enough to upset the whole finely balanced and rapidly spinning applecart.

I am sure some of our aviation guys will know.

Edited By Hopper on 15/08/2022 08:04:36

I find at least 2 a year on my 50 acres of fields so hate to guess how many are released annually.

A party ballon is unlikely to damage a jet engine directly. There is the remote possibility of indirect effects. Such as blocking a EPR (engine pressure ratio) probe resulting in incorrect thrust indication. Even more remote some palstics can cause corrosion issues. Specifically PVC due to the chlorine content. There have been cases of blade failure from corrosion caused by smears of plastic packaging on the surface. This was due to someone pushing the blade through the bag rather than cutting the bag open.

There was a case in the UK a few years ago of a light aircraft having engine failure from a rubber ballon getting into the air intake No not all aircraft engines have intake filters. The aircraft was deliberately trying to hit the ballons as pat of a competion…..

Robert G8RPI

It's a curious element

any helium released into the atmosphere floats into outer space and is lost forever

The NTSB report for the Hopper's accident can be read here. (LAX94FA047, event occurred 11/15/1993 in Brea, California) It says:

"The National Transportation Safety Board determines the probable cause(s) of this accident to be:

THE PILOT'S CHOICE OF AN INADEQUATE CRUISE ALTITUDE OVER ROLLING HILL

TERRAIN WHICH RESULTED IN AN IN-FLIGHT COLLISION WITH HELIUM BALLOONS

AND AN IN-FLIGHT LOSS OF CONTROL FOR UNDETERMINED REASONS. A FACTOR IN

THE ACCIDENT WAS THE PILOT'S INADEQUATE VISUAL OUTLOOK."

It appears the pilot perhaps with an eyesight problem and definitely flying too low for the terrain flew into a bunch of Helium balloons and power-dived vertically into the ground with both engines running on high-power.

Possibly something like when my daughter crashed my car (not hers!). Driving along an empty dual carriage-way in twilight at 70mph, something big and black, reared up and ran under the bonnet. She braked and swerved to avoid it and hit a post causing considerable damage, but no injuries. Collecting the wreck I found an empty bin-liner in the debris; my guess is it was inflated by a gust of wind and blown into her side vision causing her to lose control after instinctively jerking the steering and braking hard. As a learner driver I remember being told to run over animals in the road rather than swerve to avoid them. The advice is probably good for the UK where most animals likely to be in the road are small, but may not be smart if the animal is a Moose or Kangaroo!

Judging by the NTSB reports Helium balloons are completely insignificant compared with small private aircraft. One accident in 1993 compared with about 4 per day in the US. Small private aircraft have a relatively high accident rate mostly because of pilot error, but also poor maintenance. Compared with commercial flight, private pilots take higher risks because they're poorly supported by training, instrumentation, and safety systems. The good news is that accidents are far more likely to kill or injure the pilot and passengers than anyone on the ground.

The accident reports make interesting reading because they almost always have an accident chain where a series of small non-critical misadventures add up to a catastrophic failure.

Not suggesting there's a particular problem with light aircraft; motor-bikes, push-bikes, marathon running, horse riding, travelling by road, and living in a city centre are also risky. DIY is quite dangerous too, yet Model Engineering rarely causes accidents. I think it's because lathes, band-saws and mills are fixed and the operator rarely gets too close. Much easier to lose control of a hand power-tool and whack one's fingers with a hammer!

Dave

Edited By SillyOldDuffer on 15/08/2022 10:45:27

I;ll bet that defrosted them rather well!

That is exactly the case with many accidents in industry too, including boilers. Faulty low water cut-off switch is disabled so that it stops putting the fire out unnecessarily. The factory Plant Engineer is demanding steam and now! Disabled switch is not repaired yet because the electrician says parts are not available until next week. But in the meantime the operator can rely on the gauge glass and separate low-water alarm switch that operates a loud horn. Factory has steam. All good!

The small wet-steam turbine driving the feedwater pump trips and stops due to speed governor worn out and a bit temperamental due to lack of maintenance over 20 years. It does this from time to time and you just stick a Brasso tin under the governor linkage and restart it before the water level drops too far. Boiler has water. All good!

But this time, the water level drops and sets off the low water alarm horn. The boiler operator is outside refilling the large chemical tank in the boiler feedwater treatment plant and backflushing the filters with very noisy pumps running right next to him, due to bearing wear. Does not hear the boiler alarm horn. Water continues to drop in the boiler inside. Disabled cut-out switch does not douse the gas fire. Water drops below top tube level. Fire continues to burn.

Tubes sag. Tubes leak. Steam goes everywhere. Boiler operator returns and sees and hears this. Looks at glass. Empty. Starts standby electric feedwater pump. Pumps cold(er) water into boiler. It hits overheated tubes. Thermal shock occurs. Tubes fracture at ends where stress is highest where they were expanded into the tube sheet in manufacture. Several were over-rolled and a bit thin. One has gouges in it where the expanding roller got stuck. Others, and the tube sheet itself, have 20 years of corrosion around that area, due to the water treatment plant is always on the blink and water chemistry is very often wrong and thus corrosive. The inspector commented on this corrosion last year but passed the boiler as safe to use.

Steam and very agitated water rush out through the fractures. Water is at about 350F at 100PSI before it exits. At atmospheric pressure it flashes off instantly into steam and expands to 1600 times its volume, taking the wall out of the boiler house.

Who is to blame?

Edited By Hopper on 15/08/2022 12:25:38

That's what the union rep said.

It is a waste of a limited rescource to use helium for trivial things like party balloons, there are scientific uses which are much more important. Helium was named because it was detected spectroscopically in the sun before being discovered on earth.

I suspect that "PILOT'S INADEQUATE VISUAL OUTLOOK" is almost certainly an implication by the investigators that the pilot's monitoring of his visual environment wasn't sufficient (in Britain the word used is Lookout), rather than that he had an eyesight problem (he was required to wear corrective glasses). Quite how they knew this is another matter – this investigation report seems particularly short for a somewhat inexplicable fatal accident, with, for example, no hint as to what height the aeroplane might have been at.

There is no mention of balloon fragments entering the engines (or any other mechanical malfunction), so this idea may have been a product of over-active journalistic imaginations in the LA Times.

Edited to remove smiley

Edited By Andy Stopford on 15/08/2022 20:24:46

What depth of cut do you envisage Dave ? Carbide tooling I assume ! Noel.

Couple of points on this.

To get the details from an NTSB investigation you need to look in the "docket" which is generally available on-line and can have lots of ananlysis and data. As an example, one of my projects is a Honeywell (formerally Garrett) gas turbine engine. It's a GTCP-35-150. I've had similar engines before and manuals for the older versions are available. This particular variant had electronic control. and manuals have not been released. There is a current operated electro-hydraulic (fuel is the fluid) valve that controls the engine. A ECU elsewhere on the aircraft controlled this. Of course I don't have this. As I'm an electronics engineer I have issues bout building a PID controller but certain vital data eluded me. The most critical was the current through the servo valve control coil. Too much and you burn it out. I found an NTSB report of a ground incident where the turbine wheel explooded due to over-seed fron de-icing fluid getting in the intake. In the docket was a scan of the computer print out of the ECU's bench test. This not only gave me the valve currents for this ECU but the limits. It also conformed my calculations for the number of teeth on the gear that is sensed to measure RPM. Pricless info.

On the crash at Cranfield the thng that interested me was that they basically moved the whole test programme to the UK and used a single engine aircraft to take advantage of a new regulatory class "E conditions" so they were designing, buildin and fly this aircraft with no organisational approvals at all. IT was all signed off by a single enginee who was not even an employee.

Robert G8RPI.