0 votes
asked by (17 points)

While flying the Zibo 737-800 mod the plane about every 1 out of 2 times pitches up, stalls and crashes it happens. I tried to see if anyone had the same problem and saw one post which said something about de-icing the plane or something, tried it but still didn't work. It happens consistently at the top of descent. The same thing happened today and just as it happened before it crashed I quitted so it should be somewhere below on the log file, tried to find the problem but couldn't understand anything in the log file. If anyone is knowledgeable about this subject or could give any advice, please do as It has really been annoying me for this past week trying to find a solution, thanks in advance.http://questions.x-plane.com/?qa=blob&qa_blobid=4030393024380127746

2 Answers

0 votes
answered by (613 points)
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Best answer

Form your description, you could be right that icing may be contributing to the loss of control and crash.  Though it is odd that it always occurs at the top of descent.  And you said you have turned on the Wing and Engine Anti-Ice on the overhead panel?  What’s the outside temperature (TAT) shown on the Engine Display?

Inflight icing generally forms between 0 and -20 degrees C, with visible moisture (e.g., rain, in clouds).

commented by (613 points)

Have you tried posting on the .org Zibo forum regarding the control issue?  It is frequented by plenty of experienced users.  Since the problem is repeatable, perhaps you can post a short video of the crucial moment and see if you can get an answer of whether it’s a known bug.

As for the default B738, I took the latest rev (11.36r2) up to cruising altitude a couple of times and had not encountered any “beeping” issue.  Since you've eliminated cabin altitude as a suspect, sorry, I can’t think of any reason.

commented by (613 points)

P.S. I just noticed in Image1, the IAS was set to 330 in the MCP.  That’s pretty high!  In fact, when I tried it in the Zibo, it had limited my setting to 275 (at FL370).  You can also see that the redline for the IAS was indicated at ~280 kt.  Moreover, I believe the 737-800’s max speed is Mach 0.82.  The PFD was indicating 0.90.  I know the aircraft at this point had already gotten out of control, but what was the IAS and Mach speed just prior to that point.

My guess is the aircraft was suffering structure damage from overspeeding.  As I mentioned, the Zibo doesn’t seem to display any message to announce airframe damage, it simply goes unusual attitude on you when that happens.  I’d try easing back on the cruising speed to see if that would make a difference.

commented by (17 points)
Hello, sorry for the late reply,

On the flight I took the image I had reached cruise level and had a speed of about 330 as shown on the autopilot, due to the stall it dropped, so you'r right on that.

Also just to confirm, I need to make sure the speed stays below 280kt and I'm below the red line as well as that the PFD indicates below 0.82 for my next flight, right?

If so I am quite sure it's the solution as it explains

Why it happens near descent and cruise timing as it's the time the engines have enough time to reach top speed and for damage and structure damage to occur.

It also explains why it happened 1 out of 2 times, as the only time it didn't happen was on a rather short flight and the speed didn't have enough time to reach 330kts or above 280kts and also it didn't have enough damage from overspeeding to be out of my controls.

I thought the speed limit was 350kts as only then the alarm for it would occur on the B737 on the Zibo mod and on the default and also didn't really expected it to be that realistic for strucure damage to occur as well as the loss of control. Will try it out on my next flight and get back soon, thanks for your help!
commented by (613 points)

The Indicated Airspeed speed limit for the B738 (others as well for that matter), decreases with altitude.  Because the reading is “indicated”—not the “True” airspeed.  Up at FL370, 330kt IAS would probably be supersonic!

I don’t know how “realistic” is the simulation regarding overspeed structural damage.  I only hope it’s more forgiving than that in the real aircraft!

commented by (17 points)
Hello,

I just completed about 500NM of flight hours (of just takeoff and cruise, will complete it tomorrow) staying under Mach 0.82 and it didn't happen as expected from my last post, which was reliving, thanks for your help!

I think I now know how to operate it while staying under Mach 0.82 after trying it while flying, it changes according to my pitch and calculates it with my TAS, so I basically have to stay under the red line.

I suppose the alarm on the default 737 is also regarding this issue.

I am almost 100% certain this is the resolution to the issue but will do a couple more flights and ensure it is resolved and will get back in a few days, thanks so much for taking the time to help. Would probably not have used the Zibo and default 737 without your help, therefore I'm very thankful to u for helping a stranger!
0 votes
answered by (5k points)

Hi ToyMasker,

You need to read the answer provided in the following link found at https://questions.x-plane.com/26025/intermittent-frame-rate-drop

Glenn

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