Oh no .. not another Lion Air incident

4G. It makes me wonder what the G load would be if you just didn't flare at all? 800 fpm at say 150 kts. Any takers on this math problem?

 

Lou- Too hard to calculate when you add in ground effect and strut compression, but 800'/min= 13.3 fps with no slowing and the max descent rate on landing for the F-35C is 26.4 fps, about twice that. Navy test pilots have said they really have a hard time getting that high an impact speed because it is so violent it usually takes them two or three tries to land that hard.

Sounds like for a 4 g impact, descent rate would exceed your 800 fpm by quite a bit.

 

Yeah, I figured it must've been quite a bit more than that. Just used half the airspeed rule (actually ground speed) to figure the required VS required to follow the glideslope. So say around 160 kts = 800fpm for approach. Then no flare at that rate. I'm curious what that would give.

He obviously hit a lot harder than that.

 

But it makes you realise how tough Boeing aircraft are. I feel more comfortable sitting in a 737 inside a thunderstorm, than sitting in a boat on Sydney Harbour!

 

When I was working at Boeing some of the stuff was designed to as much as 14G. A great amount of skill and experience goes into designing the wings for gust loads as well as static loads and they never skimp on it either. Most difficult is to build a wing where you are getting loads going in opposite directions in turbulence

 

Lou- If we know how far the struts compress, we can calculate that.

 

Didn't Lion Air receive a ban from European airspace?

 

You would need the rate of compression too. It's not linear.

 

Zack- It would be pretty close to instantaneous at that rate of descent.

 

It occurs to me that the discussion here should be more about why in the hell this guy DID IT than whether or not the transport jet could take it and survive.

It is starting to look like this airline should be closed down, at least until they can decide to learn how to fly safely.

 

800 fpm is 13 fps.
Struts on passenger aircraft are pretty big, assuming the travel is 6.5 feet, it would take half a sec to compress fully.
From s= ut+1/2(a)t^2, and u = 0:
a = 2s/t^2
= 13/0.25
= 52 fps^2

From F=ma, assuming mass and knowing a, we can calculate F. Divide by g to get multiples of g's. So, who can finish this to get a rough idea of the g loading?

 

Zack- That is a little less than 2 gs.