SurClaro Flight Simulator Resources

[Rhythmosaur]

If I had not been flying real gliders, I would not know it either:

The speed gauge and the variometer get their data from a small tube on the outside of the plane. The wind blows in. On the opposite site, there's another hole in this tube. I should know more details as it belonged to my pilots education, but I just can tell from the difference of pressures the data is translated into what you see on your panel.

When you are flying undercooled water or even icy clouds, this tube will be blocked by condensing undercooled water turning to ice, or by ice itself. This effect is simulated, even in FS02. As a result, your gauge will point Zero, and when you are flying with autothrottle, the engines will roar to the max in order to accelerate and reach the target speed INDICATED. Depending on your altitude, it can happen that you just exeed Vne (Velocity Never Exeed) and therefore overstress the frame...

Since a great french fellow developed this technik that still is in use with the big planes, it is called Pitot [Peetoh] tube.

The heaters prevent ice blocking the tube.

Some planes don't have the switch. That's why I advised you to leave it turned on when saving a standard flight. However, there's the possibility to use a shortcut.

The Rhythmosaur

[Commander Cool]

Thanks Rythmosaur but there is still one thing that confuses. What about the planes which do not have pitot heat won't their airframe become overstressed?

[Insured Disaster]

Well, the pitot heat and tubes themselves do not result in overstressing an airplane. However, if you leave the airplane on autothrottle, it will think the plane is flying slower than the "selected" airspeed and thus attempt to correct that, to the point of exceeding the structual limitations of the plane and destroying it.
Suppose you were to discover one flight that your pitot tube had frozen up? First, shut off the Autothrottle, then check your altimeter, VSI, and power indicators (tachometer or N1 gauges, depending on your air plane) , then turn on pitot tube if equipped. Remember, fly the plane first, then trouble shoot.
If you are climbing, you can decide how much thrust you need for your rate of climb, and use the power indicators to adjust thrust accordingly. If you are level, use thrust accordingly. If you are descending, (you guessed it) use power indicators to adjust your thrust, i.e. you are not going to need full power to descend in a 747. But how will you know if you are going too slow? Things like trim settings, control response and pitch angle will help you. In level flight, (no climb or descent) the pitch of your nose indicates speed to some extent. Low pitch= high speed, high pitch= low speed. Hight and low speed is relative to the plane you are in, 120 is "high" in a cessna 172, but "low" in a Lear.
If you cannot clear the pitot tube, you must return to the airport, as it powers the airspeed indicator which is a "required" instrument.

FYI= The pitot tube has two holes in it. One is on the front, where the air comes in. The other is at the "elbow" of the tube and it is literally pin sized. It allows water to drain out. If both of these holes are blocked, the airspeed indicator will act like an altimeter. So if you climb, so will the airspeed. This type of blockage has resulted in many crashes as the pilot begins to climb faster and faster, thinking that he is accelerating. Finally, the nose is pulled up to a stall, and in IMC conditions, this can be very dangers. The other way a crash can result is when the plane descends and the airspeed indicator (acting as an altimeter due to blockage, remember) starts to show a decrease in speed, and the pilot noses over more and more, while his airspeed indicator continues to show a decrease, where as in fact his speed is increasing, often to the point of structural failure. I don't think MS models this particular type of blockage, which is a shame, as it is hard to recognize (you wont notice anything wrong unless you climb or descend from the altitude at which the blockage occured) and is the type of thing to practice in a simulator. MS models just the front air inlet being clogged.

[Commander Cool]

Thanks Insured Disaster. That has really cleared the air or should I say blockage! Wow that was a bad joke!

[cruas]

I read on another forum about the great interest that exists for "Pitot" and "Static Ports". This two elements serve to transmit information to the aircraft (airspeed). On the mentioned forum somebody posted information regarding an Aeroperu Boeing 757 that crashed 30:59 minutes after takeoff. It made me mad that there was a lot of wrong information posted. Somebody even tried to simulate the situation on FS2002 and posted that he was able to land the plane... of course he may, but he was not considering that crew was not able to disengage the the auto-throttle during the short and stressing flight.

Everything started on October 2nd 1996 in Pasamayo-Perú (Pacific Ocean) after takingoff from Jorge Chavez Intl. (LIMA-PERU).

Before this accidente Boeing did not had a procedure released for this kind of emergency. The Captain's Instruments were going one direction while the F/Os were going to another. Additionally Autothrottle could not be disengaged.

As mentiond on this forum by Insured Disaster, it may me possible to destroy the plane in flight if you leave the autothrottle switched on. It seems easy to to solve a situation when the plane's pitot tubes are blocked (ice or tape!), first of all if you are flying with AT turn it off! But, what happens when additionally your "Static Ports" are covered or blocked... The FMC will go crazy by denying to switch AT/AP off, the plane will try to stabilize (assigned VSI, Flight Level and Speed).

If you want to try it, depart from Jorge Chavez Intl. (LIMA-PERU) winds calm at 00:40 local time (Destination Santiago - Chile), use TO/GA climbing FL290. Just after take off (V1 plus 10 or 20) kill your Pitot Tubes and Static Ports. Once you noticed the failure proceed right to the Pacific Ocean using following the STAR for Jorge Chavez Airport. Do not turn your AP/AT (TO/GA) off in order to simulate the situation of flight AP603.
If you are able to mantain the plane flying for more than 30 minutes clircling on the HOLD Path you may consider yourself lucky, if you are able to land after 30 minutes you may be considered a total expert.

BUT, YOU WONT!!!

I have attached the translated transcript of the last 30 minutes of Flight AP603... Good Luck!!!

I knew people on the plane... the crew was experienced but the situation was abnormal and not even Boeing though it may happen, but it did. After the investigation was over Boeing released the procedures!!!

If somebody wants to have more information, let me know!

carloruas@hotmail.com

[guido90]

Thanx for the transcript, I was looking all over the net, couldn't even find a spanish version. My sources tell me that the Autopilot and Autothrottle were not even turned on. It couldn't be turned on because AP needs at least two of the three instruments to show the same value, but in the aircraft all of the instruments were showing diffrent values. And PITOT TUBES WERE NOT BLOCKED BY TAPE, only the static ports.

[guido90]

...another thing: that transcript, who translated it to english, something looks wrong in the part 5-7 min of flight.

[Rhythmosaur]

@cruas:
Please let me just tell you something you cannot know to prevent an unpleasant situation:

A great fellow out here whose name is classified, once provided information about crashes and invited to discuss investigations on them.

The result, unfortunatelly, were juvenile comments and reactions like you described them, alongside with - like you also said - false data. To the point, unprofessional chases for reasons ("I'd have landed this plane!", "The pilots were idiots"...) without thinking about the victims and their families. More brief: Annoying.

We ended up with it by a consent to aviod discussions like that and leave investigations to the pros.

So PLEASE:

Keep this in mind when you carry on with this thread. As you described your experience at the other site asannoying, too, I'm sure you can live with this. To tell the truth, we at SurClaro are one step (at least) further and that's why people come here... :D 8) :twisted:

The Rhythmosaur

[cruas]

Guido90,

I've attached th original transcript used on the investigation by the FAP (Fuerza Aerea Peruana / Peruvian Air Force)...

As you said, only the static ports were found covered with tape, on the other hand nobody knows if the pitot tubes where covered too (they were not found intact and one was missing).

After Boeing released the procedures some tests have been done on 757 Simulators, it is vere possible that at least one of Pitot Tubes may have been covered. On the other hand this has become part of the training in order to prevent it to happen again.

Additonally I'v attached an Alarm Activity File that shows the different type and not logical way the plane systems were working.

The intention of this post is show what may happen if the Pitot Tubes or Static Ports have a malfunction or if you forget to heat them up.

Take care!

[guido90]

Cruas wrote: "As you said, only the static ports were found covered with tape, on the other hand nobody knows if the pitot tubes where covered too (they were not found intact and one was missing)"

If the pitot tubes were covered, no airpressure would be mesured, therefore NO SPEED, and they were overspeeding, stalling, mach-timming, and rudder-ratio... so I say again, the pitot tubes (ised in combination of the static ports for measuring speed were not covered with tape)

Thanx for the attachments.

[Rhythmosaur]

cruas wrote:
The intention of this post is show what may happen if the Pitot Tubes or Static Ports have a malfunction or if you forget to heat them up.

Take care!

I don't know what the other mods think, I myself highly apprechiate that. Goood work. As long as it does not tilt to what I mentioned before...

[Insured Disaster]

"The most insidious of these failures is the total blockage of the pitot sytstem. . . Blockage fo both the ram air inlet and the drain hole causes the airspeed indicator to act like an altimeter, moving in the opposite direction as you would expect the airspeed indicator to move in a climb or descent. Inflight breakups of aircraft have occurred because the pilot dove the airplane at speeds exceeding red line while the airspeed indication dropped toward stall speed."

-Excerpt from the Jeppesen Instrument Commercial Manual, 2001