{"id":4822,"date":"2019-07-31T10:44:16","date_gmt":"2019-07-31T05:14:16","guid":{"rendered":"http:\/\/themagnumgroup.net\/Blog\/?p=4822"},"modified":"2020-04-01T15:59:55","modified_gmt":"2020-04-01T10:29:55","slug":"why-the-737-max-tended-to-tip-upwards","status":"publish","type":"post","link":"https:\/\/themagnumgroup.net\/Blog\/why-the-737-max-tended-to-tip-upwards\/","title":{"rendered":"Why the 737 MAX Tended to Tip Upwards"},"content":{"rendered":"\n

The Unexplained<\/h2>\n

Boeing’s ill-fated 737 MAX series planes have larger engines<\/strong> than the earlier 737NG series. You may have wondered (as I did) why those larger engines caused MAX planes to pitch upwards<\/strong> during takeoff, necessitating the disastrous MCAS software. Basic logic suggests that the new, heavier engines would tend to make the planes pitch downwards<\/em>.<\/p>\n

Being a curious engineer, I started researching and found enlightenment on the subject, which I would like to share with you.<\/p>\n

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Why Larger Engines?<\/h2>\n

The main feature that differentiates the MAX series from earlier 737s is its larger engines. Boeing needed to put in larger engines to make the 737s more fuel-efficient.<\/strong> 1<\/a><\/sup> They had to do this to stop American Airlines from ordering a huge batch of A320neo<\/strong> planes (which were more efficient than the contemporary 737NG) from Airbus and order on them instead. 2<\/sup><\/a> <\/p>\n

The Surprising Explanation<\/h2>\n

As is evident from the image below, the new engines are mounted higher<\/strong> than in the previous 737 series (737NG). They are now in line with the wing, and in fact, some parts of the engine housing are actually higher<\/em> than the wing (not visible in the image).<\/p>\n

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At normal speeds and normal thrust, the larger, heavier engines do not create any additional aerodynamic phenomena.<\/p>\n

However, at an angle of about 14 degrees coupled with higher thrust, the engine casing begins to act as a wing<\/em> <\/strong>and starts generating additional lift, pushing the nose of the plane upward, as shown in the below diagram:<\/p>\n

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And of Course…<\/h2>\n

Boeing installed software<\/strong> (called MCAS) to automatically push the nose down in this situation, which, coupled with a defective sensor, resulted in the deaths of more than 300 people.<\/strong> But that’s another blog post.<\/p>\n

I hope this explanation was of value to you. Please feel free to put down any thoughts you want to convey in the comment box below.<\/p>\n

As Sir Francis Bacon is reputed to have said, “Knowledge is Power.”<\/p>\n

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Further reading:<\/p>\n

Boeing\u2019s automatic trim for the 737 MAX was not disclosed to the Pilots<\/a><\/blockquote>