5 ms·

The cruising airspeed of an airplane is faster than its landing speed. I don't know if that alone is enough to rip the engine off the wing, but it's something t

The cruising airspeed of an airplane is faster than its landing speed. I don't know if that alone is enough to rip the engine off the wing, but it's something that it sounds like you did not consider in making your point. [EDIT remove "roughly speaking an order of magnitude"]

AshleyGrant 8y ago
>The cruising airspeed of an airplane is roughly speaking an order of magnitude faster than its landing speed. No. No it is not. 787 approach speed is 145-153 knots. It does not cruise at 1400+ knots.
- gugagore 8y ago
  Thanks for bringing more precision to the conversation (really). What would you like to call the factor? 3? Call me a weasel, but I was hoping "roughly speaking an order of magnitude" would go down to 3. I suspected it was comfortably above 2. Am I right about that?
  - a1369209993 8y ago
    > I was hoping "roughly speaking an order of magnitude" would go down to 3. I'd call that half a order of magnitude, considering log₁₀(3) is around 0.477. So you're off by more than a factor of two.
    - gugagore 8y ago
      You know, I considered saying that the "roughly" buys me a factor of two in log space. I didn't want to be that person, but I'm glad you were ;).
      - a1369209993 8y ago
        It's surprisingly non-trivial to pin down exactly what the 'correct' scale[0] for a given measurement is. I do agree about "roughly" generally being up to a factor of two in the appropriate scale[1], although I'm the sort who thinks a 19% increase (or 16% decrease) should be called a quarter of a factor of two. 0: Uniform, linear and logarithmic are obvious candidates, but depending on the domain you can end up with some really wierd scales (eg floating-point ULPs, which can look logarithmic or linear, but aren't either). 1: hence > So you're off by more than a factor of two.
  - billforsternz 8y ago
    3 is half an order of magnitude (because it is a good approximation to 10^0.5)
  - Tushon 8y ago
    re go down to 3: Use different words and see if you think it was reasonable roughly 10x going down to 3x would also mean it would go up to 17x. That's a pretty wide range, so I don't think that order of magnitude is going to ever really be similar to 3x of something on the basis of what it means.
    - gugagore 8y ago
      but what about a rough order of magnitude? There is definitely some qualifiers you can put on "order of magnitude" to make it include 3.
      - abduhl 8y ago
        "within an order of magnitude"
7952 8y ago
It seems unlikely that a jet engine could rip itself off the wing in any scenario based on thrust alone. The forces involved are not that large.
- jsjohnst 8y ago
  Your wording makes it where you aren’t factually wrong, but a plane was in fact wripped apart due to the thrust reverser engaging on one engine of a 767: https://en.m.wikipedia.org/wiki/Lauda_Air_Flight_004 https://en.m.wikipedia.org/wiki/Lauda_Air_Flight_004
salawat 8y ago
The difference isn't that large in the grand scheme of things. The engine mount would have to be able to fail in it's operational envelope in order for the reverser kicking in to be realistic. In fact, the reversed kicking in would decrease the loading on the aircraft by decreasing it's airspeed. This isn't a case of acceleration being able to break the mount from the frame. If it ever could, one wouldn't want it on the plane in the first place. Doesn't mean you couldn't ruin your day with it, but it isn't an instant catastrophic failure either.
- jsjohnst 8y ago
  > but it isn't an instant catastrophic failure either. Read the accident report and follow up on Lauda Air Flight 004. Boeing specifically was forced to issue a statement that it was virtually impossible to overcome a catastrophic failure outcome from a thrust reverser deploying at cruising speed.
  - salawat 8y ago
    I stand corrected. Way to go Boeing. Seems like that should have come up in a design meeting at some point.

AshleyGrant 8y ago

>The cruising airspeed of an airplane is roughly speaking an order of magnitude faster than its landing speed. No. No it is not. 787 approach speed is 145-153 knots. It does not cruise at 1400+ knots.

gugagore 8y ago
Thanks for bringing more precision to the conversation (really). What would you like to call the factor? 3? Call me a weasel, but I was hoping "roughly speaking an order of magnitude" would go down to 3. I suspected it was comfortably above 2. Am I right about that?
- a1369209993 8y ago
  > I was hoping "roughly speaking an order of magnitude" would go down to 3. I'd call that half a order of magnitude, considering log₁₀(3) is around 0.477. So you're off by more than a factor of two.
  - gugagore 8y ago
    You know, I considered saying that the "roughly" buys me a factor of two in log space. I didn't want to be that person, but I'm glad you were ;).
    - a1369209993 8y ago
      It's surprisingly non-trivial to pin down exactly what the 'correct' scale[0] for a given measurement is. I do agree about "roughly" generally being up to a factor of two in the appropriate scale[1], although I'm the sort who thinks a 19% increase (or 16% decrease) should be called a quarter of a factor of two. 0: Uniform, linear and logarithmic are obvious candidates, but depending on the domain you can end up with some really wierd scales (eg floating-point ULPs, which can look logarithmic or linear, but aren't either). 1: hence > So you're off by more than a factor of two.
- billforsternz 8y ago
  3 is half an order of magnitude (because it is a good approximation to 10^0.5)
- Tushon 8y ago
  re go down to 3: Use different words and see if you think it was reasonable roughly 10x going down to 3x would also mean it would go up to 17x. That's a pretty wide range, so I don't think that order of magnitude is going to ever really be similar to 3x of something on the basis of what it means.
  - gugagore 8y ago
    but what about a rough order of magnitude? There is definitely some qualifiers you can put on "order of magnitude" to make it include 3.
    - abduhl 8y ago
      "within an order of magnitude"

7952 8y ago

It seems unlikely that a jet engine could rip itself off the wing in any scenario based on thrust alone. The forces involved are not that large.

jsjohnst 8y ago
Your wording makes it where you aren’t factually wrong, but a plane was in fact wripped apart due to the thrust reverser engaging on one engine of a 767: https://en.m.wikipedia.org/wiki/Lauda_Air_Flight_004 https://en.m.wikipedia.org/wiki/Lauda_Air_Flight_004

salawat 8y ago

The difference isn't that large in the grand scheme of things. The engine mount would have to be able to fail in it's operational envelope in order for the reverser kicking in to be realistic. In fact, the reversed kicking in would decrease the loading on the aircraft by decreasing it's airspeed. This isn't a case of acceleration being able to break the mount from the frame. If it ever could, one wouldn't want it on the plane in the first place. Doesn't mean you couldn't ruin your day with it, but it isn't an instant catastrophic failure either.

jsjohnst 8y ago
> but it isn't an instant catastrophic failure either. Read the accident report and follow up on Lauda Air Flight 004. Boeing specifically was forced to issue a statement that it was virtually impossible to overcome a catastrophic failure outcome from a thrust reverser deploying at cruising speed.
- salawat 8y ago
  I stand corrected. Way to go Boeing. Seems like that should have come up in a design meeting at some point.