A little more depth on the anti-ice system



This is the center of the F/E panel. There are 4 amber lights and a test switch and a test button. This panel is related to the wing anti-ice system.
In my last post I talked about the anti-ice panel on the pilot's overhead. On that panel, when you turn on the wing anti-ice you are routing bleed air from the engine through the strut into the aircraft in the aft stair part of the plane, then up the keel beam to the wing anti-ice duct which routes hot air to both wings to anti-ice the leading edge of the wing. Either or both engine one & three can supply wing anti-ice. In light icing conditions one engine would be enough to supply enough air to keep the wing clean.

This overheat panel in the center of the F/E's panel is there to monitor for hot air leaks. If there was a leak in the bleed air duct of the number engine around the strut area it could be large enough to light the amber warning light on this panel. The ENG 1 STRUT light would be on and the checklist would be used to try to isolate the leak by turning off the number one engine wing anti-ice valve. If the valve got stuck in the open position, then the thrust could be reduced to try to lower the bleed air temp. The next step, if that did not work would be to shut down the engine. You would still have the ability to anti-ice the wing from the number three engine. Check valves prevent the other engine's air from entering the supply duct of engine one.

In the middle of the three overheat lights there is one marked - LOWER AFT BODY. This light is there to protect the keel beam area in the event of a duct leak of the wing anti-ice system. Since this is a fairly large area, it may take a bit of time to heat up and it could have other manifestations such as an aft cargo overheat or very warm floor in the aft passenger cabin. Once the anti-ice valve is turned off, it could take a while for the area to cool enough for the light to go out.

The left side of the panel is the Wing Anti-Ice Auto Trip off system. If the wing anti-ice duct were to rupture in the pressurized area of the plane, high pressure bleed air would enter and pressurize the cabin. This system would sense the increase pressure and trip the wing anti-ice to off. If the break was large enough this could cause a loss of cabin pressure. Fun, hun?  

The parts of the wing that are anti-iced are - leading edge flaps (2 thru 5), fixed inboard wings above the leading edge flaps and the upper VHF antenna this is a mix of high and low pressure air. Anti-ice is more effective with the flaps up since the air has less area to keep hot. The hot air is dumped at the end of each wing.

Remember, the green lights on the anti-ice control panel are what Boeing calls valve agreement lights. If the switch is in the off position, and the light is green, then the valve is closed. same for open. The blue lights (fuel panel) are in-transit lights. These lights show when the valve is moving to the selected position.

Lou




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CoolP, the worst icing I saw was in a holding pattern at about 6,000 feet, south of KORD. The temps were just a bit below freezing and since we were slowed to get ready to leave the holding area for the approach we had some flap out. It seemed to take a bit of extra power to hold altitude. When I turned on the inboard landing light we could see a pretty good load of ice on the wiper nut. This could have been a problem for a rubber boot plane, but the 727 had plenty of hot air to keep the ice off the wings and engines.

You know its true, the CS planes are pretty well done for the cost of the model. The more I play with the planes the more impressed I am with this group in Captain Sim.

Each airline had slightly different temp numbers for the use of anti-ice, but the ones I remember were: when the temps are between +10C and -40C and there is visible moisture (fog, mist, rain, clouds) engine anti-ice should be turned on before entering the area. Of course, anti-ice was off during engine start, but as each engine was started and reached idle RPM, the anti-ice was turned on and left on until the need was no longer there. As the plane would speed up after takeoff, you had to keep an eye on the TAT so as not to do damage to the engine. If the TAT reached +11C you could turn off the anti-ice. Some times during climb, pilots would keep the speed up to make the TAT stay above the +10C to obtain a better climb. Remember, the 727 was not a great climber, so every bit of EPR helped. The difference between SAT (static air temp) and TAT (total air temp) or ram rise was as much as 30 degrees C at higher speed of cruise. The 727 had a Rosemount Temp Probe with 100% recovery. The 707 was an older plane and had a temp probe that required a bit of math to obtain TAT.

In the descent there were a few times that the RPM had to be kept above 70% N1 to insure enough bleed air for the anti-ice, but more than likely it was the F/E who would need a bit more RPM so as not to loose the cabin since the planes leaked like a corn crib.  

You only needed to leave the flaps down if you landed in a bunch of slush or very wet snow. This was so ice would not get packed into the flaps and flap track areas.

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Here is another little item that is related to icing in a way...



These little devices are found on most planes that can fly faster than my J-5 Cub. They are static discharge wicks. In this screen capture of a CS-707, you can see a small cluster of them. The small plastic rods have a very thin wire embedded through the center of the plastic and bonded to parts of the plane, normally at the end of the wings and stabilizers. The purpose is to bleed off the static charge that the plane builds as it flies through the air. Higher charges build during flight through water and ice. since the plane is stripping electrons and building a big charge. One of the first signs of a very high potential is St. Elmo's Fire. The area around the windshield and wipers sometimes would glow with a blueish light and look like mini lighting dancing around the plane. Some times the charge builds so fast that the wicks cannot bleed off the charge and a static discharge occurs. Basically, it is a lighting strike from the plane to the surrounding air or cloud, and can be pretty exciting!    At times I have seen it do some damage to parts of the plane. The static charge builds faster in ice crystals than most other types of moisture.

Lou

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Bruce, I think I just might do that! 

Lou

I love your storys Lou. My Dad was a pilot for TW express,a dn flew the Beechcraft 1900, before he was laid off. He said all the passengers had to go to the bathroom, since the 1900 was just 19 seats! He had people come into the cockpit, and you know what into bottles

Thanks again, Lou.

How long was your longest holding in those 40 years?
They always say that they want to get planes out of any holding as soon as possible, but I remember some busy (weather related) New York stories for example, speaking of far more than "as soon as possible".
Isn't it big fun to fly racetracks for hours?   Especially without an LNAV device doing the correct steering for you.


Did you take any pictures of St. Elmo's fire by the way?

CoolP asked: How long was your longest holding in those 40 years?

Isn't it big fun to fly racetracks for hours?   Especially without an LNAV device doing the correct steering for you.

I think the longest hold was one time coming into KJFK from the south. We held at about five different holding patterns. The total time was about 3 hours +. But hey, we get paid by the flight hour!  

Holding in the 727 was easy...OK F/O, it's your leg!  

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Did you take any pictures of St. Elmo's fire by the way?

You know I never did, but if I did here is what it would look like...



Sometimes the fire would just be in the sharp corners of the window, and other times it would dance around the windshield wiper nut. One time in the 747 climbing out of KJFK in rain the St Elmo's looked like a real bright landing light out of the nose and then BANG a discharge to the air. This stuff is very cool. Only one thing cooler is the Aurora.

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One night while flying to Stockholm out of New York we were flying in a 767-200 at about 66 degrees north and the light display was actually south of us - and wild!



Notice Orion in the left of the picture. The three belt stars are easy to find and Betelgeuse the bright red-yellow giant star, just above the three belt stars, which makes up Orion's right shoulder.

Lou

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Not too much holding now unless something weird happens. The time with the long hold was a long time ago. Started holding at high altitude so fuel burn was not too bad. It was just thunderstorms with some shifting winds that required constant runway changes. Every time they turned the airport around it took a while to get the flow back in line. Took all the fuel I could and still be legal for landing. The 757 was good at that.

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How about a look at the gear and anti-skid system?

The gear on the 727 and to some degree the 707 was fairly simple. After takeoff, with a positive rate of climb, you would reach over and select gear up with handle with the little plastic wheel. As you pulled the handle out of the down detent and moved it up a bunch of things happen. First you operate a cable and pulley system that opens a sequencing valve. The gear doors swing open and when they reach the full open position the next sequence is to open the valve to operate the landing gear. As the gear begins to move a shot of in-flight brakes stops the wheels from turning. Then as the gear reaches the wheel well, it hits a stop and the gear up-locks engage. As soon as the up-lock is satisfied, the next sequence is to close the gear doors. In the original 727 design, the nose wheels had brakes. Later mods took the brakes off the nose wheel and wheel stoppers, like the 707 were installed. The big difference was the loud noise of the wheels hitting the stoppers and the smell of burning rubber. As soon as the gear was retracted and locked up, the gear handle was placed to the middle or off position to remove hydraulic pressure.

To extend the gear, just reverse the above procedure, except you left the gear handle in the down detent. All pretty straight forward. The gear was moved by A system pressure in the 727 and utility system in the 707. When the gear was extended and locked down the anti-skid panel would show 5 REL lights in the 727. This showed the anti-skid system was OK, and locked wheel protection was armed. At touchdown the spin up of the wheel would activate the anti-skid system. A small generator in each wheel would generate voltage as the wheel spun. This voltage information was sent to an anti-skid computer to process. The 727 had a more advanced system than the 707. The 707 had cycling anti-skid which was more like your car. The break pressure was cycled on and off to the wheel that was showing a skid. The 727 used modulating anti-skid which is what all the modern planes now use. As you applied the brakes, the system would compare the voltage from each wheel and "modulate" or reduce the pressure to the wheel that was decelerating too fast. If the wheel stops during braking, the coefficient of friction drops to zero and you loose that wheel for braking. The modulating system would apply just enough pressure to approach a skid and then back off just enough to keep the wheel at maximum braking.



Now lets have a look at manual gear extension.

To extend the gear without hydraulic power was a chore in either the 707 or the 727. In either plane you needed to plan when you would put the gear down since once extended, it stayed down. So if you were short on fuel that could be a factor. The main gear, when unlocked, would free fall. In order to get the door out of the way a large spoon or arm would be hit by the gear falling and push the door open. The nose wheel had a cable system which controlled the door.

MANUAL GEAR EXTENSION

1. Gear lever off................................................OFF
2. Crank each gear down....................................DOWN
[each gear has a separate guide for which direction to turn the crank, it's a two step process, crank one way to unlock the gear, crank the other way to lock it.]
3. When gear down gear handle down..................DOWN
4. Visual check of gear.......................................CHECK

A crank handle is stowed on the lower, aft P6 panel. The gear extend area is just aft of the F/E seat.

In this screen capture you can see the three small doors - one for each gear - next to the F/E's chair.


In each plane you had to go back in the cabin to look through the viewing ports to see the lock indicators.
In the 727 and 707 the main gear viewing ports were just aft of the rear window exit about where the edge of the isle met the seat track. Some of the ports were pretty dirty and at night you hoped the light in the wheel well worked. The nose wheel port in the 727 was just outside the cockpit in the middle of the isle. In either case you had to rip up the carpet.

In the 707 the nose wheel down lock indicator was in the lower 41 area under the cockpit. There was a small tunnel you had to slither down through to check the lock indicator.

This is what you hoped to see through the viewing port in the cabin floor.


It could take 15 minutes to go through the whole checklist, so that is where the planing for the landing came in.

Lou

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