No Step and Painted Walkways on Wings Question

[Robert Porter]

I know that even on all metal aircraft, i.e. without fabric covered surfaces, there are areas you see "No-Step" lables, and usually there are/were painted stripes to guide people working on the surface of the wing. Were the areas that you could walk on specifically strengthened or were they just areas where internal structure provided extra support?

How much danger was there in harming a wing say of a B-17? The reason I ask is for instance the television show called Ice Pilots, routinely shows crew climbing all over the wings of DC-3 and DC-4 aircraft to remove snow with a broom and they seem to not be all that careful where they walk?

I also recently saw a video of one of the surviving B-17's in the CAF and they had a ground crewman perched on the very tip of the wing doing something to one of the lights in the wing tip?

 

[Airframes]

Basically, it depends on the specific aircraft.
'No Step' warnings are normally marked on relatively fragile areas, such as wing fillets, or control surfaces (flaps, or the wing surface above a flap, for example). They may also be found on areas such as gun or ammo hatches which, although perhaps internally braced, could be deformed if stepped or walked on.
Most aircraft are able to bear the weight of a man along the line of the wing spar, and 'walk way' lines would normally be applied along the area of the spar, or perhaps between spars, if the wing is so constructed.
Again, this would depend on the structure, and the skinning, of the wing, which comes back to your previous thread concerning stressed skin construction. It may be that a wing, for example, is extremely strong over its entire area, but some areas, perhaps aft of the main spar, although stressed and 'rigid', could again be deformed if walked on, as the internal area may not have the bracing to withstand this direct pressure (as opposed to air pressure), and could be damaged, reducing the efficiency of the aerofoil.

 

[Robert Porter]

I rather thought that would be the case, especially for control surfaces, it just seems odd that people can clamber all over wings with no apparent regard as mentioned, yet on the same aircraft there are warnings about not to do so. I suppose in the instance of the fellow I saw on the wingtip if he had spread his weight out, say by crawling, it would be fine and was probably what he did. I did not see his approach to the wing tip but he was laying prone on it.

 

[Airframes]

That's correct - on some aircraft, it is possible to 'spread the weight' by lying down. For example, on the Spitfire, the 'walkway' lines are outboard of the wing root, chord-wise, and following the line of the main spar. However, aft of the gun hatches, the wing is relatively delicate, and should not be walked on, but it is fine to lie on.
Note that the 'No Step' markings are normally applied to specific areas, and do not, normally, apply to the entire surface. An example would be the leading edge wheel bay fairing, at the wing root, on the Harvard / AT6 / Texan. This curved fairing, if dented by standing on it, could, and almost certainly would, prevent the landing gear and wheel from fully retracting.
Think of these areas marked 'No Step' in terms of a car - the vehicle might be very strong overall, but stand and/ or walk on the bonnet (hood), and it'll probably deform. As with an aircraft, this might not affect its efficiency in any way, but it has damaged the surface and, just like your car, it's not something you want - more so if it's Government Property !

 

[Robert Porter]

As with an aircraft, this might not affect its efficiency in any way, but it has damaged the surface and, just like your car, it's not something you want - more so if it's Government Property !

I can attest to that, in the service acquiring a sunburn severe enough to limit your duty, was at the commanders discretion, sufficient for an Article 15. Basically a fine, my first shirt used to say you had damaged government property by burning yourself.

 

[tyrodtom]

Anyone who works on or around aircraft knows there's certain parts you don't step on, or use as a hand hold to push the aircraft around, like control surfaces, but sometimes you're using unskilled labor. Those no step, and no hand hold stickers are mainly meant for them.
But sometimes ground crew get in a hurry, or may not be familiar with a particular aircraft, and need reminders.
There's not just a danger to the aircraft. A lot of people have walked into spinning propellers, sucked into jet intakes, or walked too close to a jet exhaust.

I know of a lot of people seriously hurt or killed by aircraft that were not even off the ground.

 

[Robert Porter]

I knew about not pushing on control surfaces etc. Just confused by how often I see folks in videos and shows walking all over aircraft seeming without regard to the marked areas.

 

[tyrodtom]

The B-17, for instance , had corrugated metal under the smooth outer metal between the mainspars, with the ribs underneath fairly closely spaced, was probably pretty resistant to ground crew damage. The B-24 had closely spaced stringers at right angles to the ribs , the covered by the outer metal. Look at some aircraft cutaways. Different aircraft, different methods.
Stress analysis wasn't as well refined in the WW2 era as it is today, some of these aircraft were overbuilt. That's how so many made it back with damage one would think would cause them to break up in flight.

 

[bobbysocks]

Anyone who works on or around aircraft knows there's certain parts you don't step on, or use as a hand hold to push the aircraft around, like control surfaces, but sometimes you're using unskilled labor. Those no step, and no hand hold stickers are mainly meant for them.
But sometimes ground crew get in a hurry, or may not be familiar with a particular aircraft, and need reminders.
There's not just a danger to the aircraft. A lot of people have walked into spinning propellers, sucked into jet intakes, or walked too close to a jet exhaust.

I know of a lot of people seriously hurt or killed by aircraft that were not even off the ground.

absolutely! on the ramp I never took my eye off of the props...even when they weren't spinning. that way i guaranteed I would watch them where they were. getting too comfortable around certain areas of an airplane can be a bad thing. we had a guy at one of our other stations chase the signed copy of the pilots paperwork right into a spinning prop. it isn't just air crew and maintenance people who are around planes but some service personnel too....de-icers, fuelers, utility (replenish the galleys, etc ) and some of those guys aren't paid well nor trained too much...there is a lot of opportunity for damage.

 

[GregP]

Believe me, they have a LOT of regard for where they are walking. If they KNOW where to walk, it might not appear that way to a casual observer, but they DO walk on the approved areas only.

 

[chuter]

I've walked (crawled, slid, rolled) all over aircraft, from fuselage to wingtip along the spar cap of a Cherokee to the (fuselage) crown of 747s, and basically, if you're not careful, you can bend the skin and the supporting flange of a rib/stringer/frame supporting it. It's a tough call because on the one hand you need to step on the supported areas of the skin but while the web of, say, a rib, can hold you, if the skin is a bit too thin it will be pressed down on either side of the rib's web and the flange where the rib is riveted to the skin will be bent right along with it. Dented/deformed skins are generally more of a performance issue than structural one but it is possible to crack the rib/stringer/frame between the flange and the web where it gets bent. So the amount of care required basically depends on skin thickness. The thinner the skin, the thinner the support structure, the easier to bend those flanges. Dents can be knocked out, sorta, but the metal is stretched a bit and isn't ever going to be exactly like it was and there is always the possibility the support flange will crack when "straightened", especially if it is a corrosion and crack prone but light zinc aluminium (7095T6) used by Japanese after '43 (and everybody else since) instead of the more common copper based aluminium alloys (24S in WW2 or 2024T3).

Sooooo ... wing walk markings show only as far as someone sitting behind a desk is willing to go to say there shouldn't be a problem walking there. After that you're on your own, he ain't responsible (they never are - lol).

 

[Robert Porter]

Sooooo ... wing walk markings show only as far as someone sitting behind a desk is willing to go to say there shouldn't be a problem walking there. After that you're on your own, he ain't responsible (they never are - lol).

Desk jockeys never take responsibility for much of anything in my experience. When I was young back before cars you know, there was a VERY small airport near my home town of Tarrifville Connecticut. The runway was so close to the little frontage road that there were occasional car strikes from landing aircraft.

But, they had 2 WWII vintage aircraft parked 10 feet off the street with no fence, which was a young boys dream come true I clambered all over them. Have no idea what they were, they were single radial engined with a Pilot seat and a rear facing backseat. I was told they were some kind of torpedo plane, they did have a huge bay in the underside and their wings folded up. As a fairly lightweight kid I stepped straight through a wing about 2 foot from the wing root. Of course I assume corrosion had something to do with it as well. These planes were in pretty rough shape but I spent many a day chasing Zero's (in a torpedo bomber probably not a good thing to do) in my mind and was an Ace many times over.

 

[Pursuivant]

In a very few cases, mostly on training and low performance aircraft, the areas where you could walk to get into the cockpit were marked with black paint or possibly anti-skid adhesive tape or period equivalent. Waxed or wet metal wings are slippery and at an angle on a tail-dragger aircraft, so there were good safety reasons for doing so this.

I'd imagine that airframe mechanics knew exactly where they could and couldn't step on a particular aircraft. On a tough aircraft like the C-47 or B-17, or when maintenance speed mattered more than anything else, they might step or crawl all over an airplane. On a more lightly-built aircraft like the B-24 with a very efficient, but not very strong wing, they'd probably be much more careful.

Another thing that you see in the cockpits of fighter aircraft is "no hand hold" on the gunsight mount, to keep knuckleheaded pilots and ground crew from grabbing the gunsight and damaging it or knocking out of alignment as they got into out out of the cockpit.

 

[chuter]

In a very few cases, mostly on training and low performance aircraft, the areas where you could walk to get into the cockpit were marked with black paint or possibly anti-skid adhesive tape or period equivalent. Waxed or wet metal wings are slippery and at an angle on a tail-dragger aircraft, so there were good safety reasons for doing so this.

I'd imagine that airframe mechanics knew exactly where they could and couldn't step on a particular aircraft. On a tough aircraft like the C-47 or B-17, or when maintenance speed mattered more than anything else, they might step or crawl all over an airplane. On a more lightly-built aircraft like the B-24 with a very efficient, but not very strong wing, they'd probably be much more careful.

Another thing that you see in the cockpits of fighter aircraft is "no hand hold" on the gunsight mount, to keep knuckleheaded pilots and ground crew from grabbing the gunsight and damaging it or knocking out of alignment as they got into out out of the cockpit.

lol - yeah, the old "no hand hold" stencil/placard. Code for "be careful when using as a hand hold, your ass is on the line". But I didn't say that, one should always follow the manual and stenciling/placarding ...

Actually, I've always said if one has to refer to the stenciling/placarding (which I've had occasion to see be incorrect, lazy painters) one maybe should rather look up the relative information first.

The absolute worst aircraft for climbing (literally climbing) on is the Corsair. It's all high-peaked-roof and no gutter - lol - so to speak. It can be very scary at times.

 

[von hahn]

Another reason that "no step" markings are there is to prevent people from walking on areas where it is potentially more likely they may fall from a height, as well as the obvious reason of preventing damage to more delicate areas of the structure. Wings and fuselages in general are quite string and certainly can bear the weight of a person