What’s their purpose once they don’t slow down the aircraft? (I’ve read a topic a few weeks ago but didn’t remember the reason)
If you’re talking about the roll spoilers on 38M, they are to slow down the speed of only one side of a plane so plane can turn more in a small circle. For example of you bank right, only the roll spoilers on the right wing will be expanded.
noo I’m talking about “flight spoilers”, their function is literally slow down the aircraft breaking the aerodynamics but this don’t happen on the 38m
The B38M is a slippery aircraft and the spoilers are rather ineffective. This was also outlined in the B38M flying guide. It’s a feature of the MAX, not an issue.
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You’re not alone in experiencing this. I even had to ask about this internally because they really are useless. In level flight with AP set to maintaining a certain speed, deploying the flight spoilers only gives you 1-2% thrust increase. It’s ridiculous but also how it should be apparently :)
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On the 26th I flew on the max and the spoilers didn’t seem useless on descent. I mean, they’re literally made to slow down an aircraft by breaking the aerodynamics, how could they be ineffective even when deployed (flight mode)
Boeing haven’t made a lot of sense these past 10 or so years, so who knows.
The information about the spoiler’s effectiveness comes directly from a source flying it :)
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Because the wing is extremely slippery. A Line Check pilot I consulted during testing stated that “The speed brakes will either give you deceleration at 1000-1200fpm descent or will allow you to maintain speed and get 1500-1700fpm” between 10K-20K.
The plane isn’t broken - it’s just how it is.
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Fair. Thanks!
and
are consistent with:
The glide ratio is the same as the lift-to-drag (L/D) ratio, and the L/D ratio is constant at a given airspeed and configuration (flaps, etc.).
So, spoilers reduce lift (L) while keeping drag (D) more or less unchanged, allowing the aircraft to descend at a steeper glide angle. This steeper glide angle enables the aircraft to maintain a constant indicated airspeed (IAS) (without acceleration or deceleration).
The glide ratio is the descent angle that will keep your IAS steady without engine power.
D more or less unchanged means spoilers don’t cause much deceleration in level flight.
edit: So, you can decelerate at a steeper decent rate with spoilers than without:
In the above you’d be descending at a somewhat shallower descent angle than the spoiler enabled steeper glide angle.
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Wow, didn’t know abt that, thanks for clearing me!
The spoilers do not have an effect on speed during descent (this was intentional, as it’s how it works in real life). However, spoilers serve two purposes: one, to slow you down, and the other, to increase descent. I haven’t flown the MAX 8, so I don’t know if either purpose has any effect on the aircraft. However, even if they don’t, spoilers also deploy on landing, so they might be added just cosmetically.
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Me casually flying the Max at 50,000 feet with 40° of flaps and a fuel flow of 2
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I used the spoilers to increase descent on the Max on a past flight because I was too high on the ILS. It didn’t make any difference compared to descending without them, so I just stored them back and pushed the nose down for a -1000ft/m rate.
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I tried testing at various speeds, weights and altitudes (nothing super formal though), and I also found little effect.
Though the theory I stated is correct I believe, testing, I haven’t yet been able to get these numbers (varying weight and IAS over the range of altitudes listed):
This, though, seems too far outside the flight model range, other than for fun:
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yeah going that high completely breaks it 😂