What in the world is causing this pressure at the back

I just realized a feature new to me and was tinkering with it while parked, because I’m a “genious”.

Didn’t realize it’d give me some troubles up in the air, I was power climbing but loosing speed, didn’t made much difference when it settled on cruise. I watched as each time temperature decreases one degree, I lost 1 knots.

So can you guess…

What in the world is causing me to have to now cruise at +50 trim on a 737-800??

Answer will come in two hours if I could make it alive to Denver guys! :D

Airspeed decreases as you climb and the air gets thinner, this is a basic observation of how airspeed behaves and doesn’t exactly mean anything because it isn’t a literal decrease in speed and momentum.

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I flew daily with trim +4, same procedures, everything.

Specially today it’s trim +50 or die lol. Something is “different” and it’s due to something I did prior to flight.

You put all your fuel in the Center Tank. I definitely have to try that myself 😂


Good one! It’s all about gravity

No cargo in the back and/or only using the central fuel tank?

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Impressively getting warmer, if not bull’s eye!

Okay, apparently just had the smoothest approach ever even under Denver winds! Maybe I was so heavy that the aircraft were just slicing through turbulence?😁

You guys were correct, @Tsumia the realities of physics as altitude increases made it very risky for this heavy brick to fly in thin air, @KonKing and @Toon you guys were right on the spot by mentioning balance.

What I did was two things:

  • I was trying to apply what I knew about precise vref calculations for take-off and landing. So I loaded a lot of fuel - over the MLW but just under MTW - for an extra mathematical challenge.

  • But earlier when refueling, I had this “great idea” to play around with my CG, so I unchecked the cargo’s synchronized option and played around with Front and Back Cargo placement, then forgot everything about it lol!

  • So… voila, a very heavy tilted to one side pendulum.

So after consulting my Boeing chart and still did a messy high powered take-off despite applying one more flaps than per usual, I quickly noticed the magenta line was way over normal, it was abnormal!

At this point I realized the implications of me playing around with the Cargo settings combined with over MLW were real - plenty of pilots on the ground will bear witness to my stupidity when I crash.

Guys the trim for a 737-800 for me has always been +4, +5 at most… this time it required +60 at first, then +50! Still, I took the time to marvel at IF’s temperature-to-altitude-to-stallspeed algorithm before I decided to do anything about it just as airspeed dropped below 175kts🤦‍♂️

Landing was surprisingly pleasant, winds don’t even matter. Switched off A/P earlier to anticipate any potential disasters ('cause of that large +50 trim problem thingy) but I must say… the whole experience was FRIGGIN AWESOME!!

…now I’m wondering whether we could cancel out large MD-11 and 747 trim settings using cargo CG alone… hmmm🤔

Btw thanks guys for participating with this fun quiz, you’ve been awesome!

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Well glad you seemed to have narrowed down your issue!

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Yes you can, crj as well.

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