Two of the three aircraft that I worked on had wiper blades. Those were the DC-9 and Sabreliner. The wiper blades were very stiff and made of hard rubber. It was very important to tighten down the tension nut while using a spring scale to make sure the blade was tight against the windshield but not too tight.
The aircraft without wiper blades was the F-111. It used engine bleed air combined with Rain-X. Plus the windshield was long and at an angle that the air flowing over it would keep it pretty clear.
On all three aircraft the windshield had anti-icing elements to keep them from icing or fogging up.
LSLGuy, thanks for confirming my assumptions. It’s one of those things that’s perfectly obvious in retrospect if you stop to think about it. I suspect that most folks would be surprised to learn that at typical cruising altitude a jet’s indicated airspeed is very much less than its true airspeed (by a huge margin!), yet it’s also obvious that this is a crucial number since it governs everything about an airplane’s aerodynamic handling. An informative spinoff from a discussion about windshield wipers!
A bit of a slide sideways for heavy iron drivers or those that know them.
1985, London to DFW, in a DC-10. I got invited up front for a bit and I trudged up hill from the cattle pens in back. This is one of my questions. I was told that the DC-10 uses the fuselage as a sort of lifting body and that is why they fly a bit nose up a lot. True/False?
The front pilot side wind screen was 1/3 de-laminated with what looked like a large flat bubble between layers. They said it was fine but I could hardly see out of it. So much for looking out of the aircraft in the airport traffic areas…???
Biggest surprise was the airspeed indicator was well below 200 and we were early in the flight ( every seat filled and lots of fuel I assume ) and that nose up thing…?? I don’t remember the actual altitude but we were high, especially for that early/heavy in the flight… I was told that was to get out of the high west winds in that area. Question = would those circumstances actually leave them that low on indicated airspeed since I see a lot of 250+ being bandied about??? If not, what was going on to have them that slow? Fuel savings due to a bad forecast and higher head winds?? Could they, would they be launching or continuing with that tight a envelope? Aircraft was not new in 1985 judging by looks.
I need edumcation about this on the DC-10.
Splain please. Middle sized words OK.
Nose up for lifting body is legit. We get about 10% of total lift from the fuselage. The DC-10 and L-1011 were famous for a nose high cruise attitude. The flight attendant whining about pushing carts uphill both ways (!) was incessant. FOr comparison, we cruise about 1-1/2 degrees nose up.
Windshield delaminations used to be pretty common. I never flew the DC-10 but we had it on the 727 fairly regularly. Usually it’d start over in a corner and slowly spread over the course of a few days-worth of flight. The maintenance limits required it not interfere with vision and be not larger than IIRC 4" across. Delaminations were an vision problem; they didn’t appreciably degrade the structural strength of the window.
I would speculate that the crew accepted something not quite kosher with the intent to avoid cancelling the flight until they got back to home base where it could be fixed. Or it was barely OK before departure and grew a bunch on your particular flight. Changing a windshield takes a day or more. On a widebody with big windows they can cost $100K each for the parts. Plus labor and lost revenue while the airplane sits waiting for the sealant to cure.
The airspeed thing is perplexing. The 747, DC-10, and L-1011 where all designed in an era of fast speeds and cheap fuel. They liked to climb at 350 KIAS to about Mach 0.85. Clean holding speeds heavy could be over 270 knots. IOW, faster than the FAA max holding pattern speed of 265 KIAS at/above 14,000 feet. They had (still have) dispensation to exceed 250KIAS below 10,000 when they’re heavy. If they get that slow they won’t climb well; too far behind the power curve.
Typically they’d retract the slats/flaps from the first notch up to clean around IIRC 220. Below that they’d have to leave the slats hanging. Heck we’re a lot slower wing (Max mach ~0.83 vice their 0.88) and we sometimes don’t retract slats until above 200 when heavy.
Fully up at cruise altitude at the slowest practical (= max endurance) Mach you might see our airspeeds down around 230 at lighter weights. I’d expect theirs to never get below about 250. Certainly not with 10 hours flying still ahead of them.
I’m going to bet something was misunderstood someplace. For sure there’s no way to know now.
Much thanks for the reply. I was always curious about the windows.
It is possible that it was 200+ instead of below 200. It was a long time ago and I was only up there for about 15 minutes. I do remember that our indicated airspeed was really low ( I have convinced myself that it was below 200 but maybe that is the one time in my life I miss remember something. { I’m sure you understand that. } ) compared to our ground speed even with the head winds.
Another interesting thing about indicated airspeed is that it gives the pilot a means to get maximum performance from the airplane. If you want to gain altitude as quickly as possible, you apply full power and hold the yoke back to maintain a certain airspeed (best rate-of-climb speed, abbreviated V[sub]y[/sub]). If there are mountains or some other obstruction to fly over after takeoff, you want the plane to climb at the steepest possible angle (best angle-of-climb speed, V[sub]x[/sub]). There’s a speed that will give the longest possible glide should the engines go out. Those speeds are listed in the operating handbook for the plane, and are a good thing to know.
At least, that’s how it works in small planes; I imagine it’s similar, although more complicated, for the large ones.
} ) compared to our ground speed even with the head winds.