Hail Damage

[Capt Groper]

Has anybody info or experience on hail damage to windsheilds / windscreens on commercial jet A/C. The damage to an A/C structure such as leading edges and engines is well documented, however little information is available on windshields. :eek:

[Al Weaver]

> Has anybody info or experience on hail damage to windsheilds / windscreens on commercial jet A/C. The damage to an A/C structure such as
leading edges and engines is well documented, however little information is available on windshields. <

For major hail encounters (stones big enough to dent leading edges) the typical damage has been radome delamination, all leading edge dents including wings, engine inlets and engine centerbodies, but no engine blade damage. In addition these events have typically also resulted in delamination of the frontal windshields while still being structuarlly sound.

SO242 DC9, LH747 and KAL747 come to mind. I'm not sure which of the structures mentioned above is the weakest since I've always seen similar damage in all structures at the same time. I'm sure there are lots of lesser events, but Ive never heard of the windshield or engine inlets by themselves.

By-The-Way, aircraft speed makes a very big difference and very few pilots attempt to penetrate big storm cells at speeds above 250kts

[Al Weaver]

These photos were just posted a few minutes ago
http://www.airdisaster.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=001139

[Capt Groper]

Thank you for your replies Iomapaseo, interesting how much damage occured to nose dome but little if and to the windshields. However, I have heard of occurances where the impared vision to the windshield required the guidance of an Autolanding to return to terra firma. I too are searching the internet, specifically for photos of windshield damage.

[Al Weaver]

Well I can tell you that they certainly did block the pilots forward vision. I remember trying to take a photo through the SO242 window to show the effect, but it was totally opaque and no discernible shapes could be seen through the window.

I tried to E-mail you but no-joy.

[Lima Xray]

In wonder at what angle big stone hails with their mass hit the inclined windscreens together with those bouncing of the upper nose looking at the dents on the upper nose section. I wonder do manufactures test this in simulation. I know R.R. throw chickens into their engines on the test rig.

Take fast jets, especially the old types, their thick windscreen on a clear day were hard to see through let alone bad weather night conditions on landing after a sortie that filled the inside of the cockpit with brown pasta….those where ‘calculated’ for birth strikes.

Would the AAIB have anything on file? :confused:

Cheers
L-X

[GotTheTshirt]

Lima-X
the same chicken test applies to windshields and these are done with actual birds.
I dont know of any tests for either airframe or engine that address hailstones.
Obviously as the loma pictures show the radome come off worst but that may be due to the impact angles.
Have been involved with quite severe airframe damage but the windshields dont seem to suffer to the same degree

[Al Weaver]

The FAR/JARs part 33.77 do specify a hailstone impact test which nobody bothers with nowadays. It orriginally came in with the SST and assumed cruise speed and a mixture of 1 and 2" size stones. It turned out that only a few minor dents were experienced on the engine blading in the test and yet no single confirmed incident of such in service.

However some new thinking was coming about on the hail mixed with rain where the stones were very small but the mush effect was causing the compressors to work so hard to process it at idle power, that the engines were being damaged internally. Thus the push for testing moved on to more complex rain/hail/mush and and the bigger birds to sort out the new engines today.

[ 03 November 2001: Message edited by: lomapaseo ]

[LeadSled]

Iomapaseo,
Who told you that. I would very strongly recommend NOT going any where near big storms.

Who said hail doesn't get to blades?

Also, stick to manufacturers turbulance penetration speeds, you will live longer that way. In the early days of jets, slowing up as per DC-6/7 etc. resulted in a number of "jet upsets", all that I know of were initially low speed loss of control, even if the final breakup was overload at high speed.

Capt. Groper, I recall going miles of course, VTBD-VHHH, many moons ago, right down over VTBU, and looked at this ripper from a very respectful distance.

Clipper 1 or 2,( that's how long ago) also a B747, didn't show enough respect, and finally did an autoland onto 31 at VHHH, due near as dammit nil viz.

It was a very sick and sorry looking aeroplane.Ever seen a HAECO beancounter smile.
Tootle pip!

[Al Weaver]

>Leadsled
Who told you that. I would very strongly recommend NOT going any where near big storms.
Who said hail doesn't get to blades? <

I have the data and the expertise and firsthand knowledge. If you happen to find another expert in your travels they will recognize the "iceman/birdman" since I was the leader of the FAR/JAR rulemaking groups regarding these subjects.