New start material strenght calculation for operating horn from crashed plane. Part 2 4

[RedSnake]

Can anyone help me check if this calculation works so far?
There are so many conversions between different units ..
The calculation is made by a free software but I assume that their calculation models are correct.

My own assumption is that the elevator is heavier at the front edge as there are hinges made of MIL 1430 N and since the lever and its attachment also are , there are also steel details on the other side and the rest is aluminum.
I have chosen to see it as a simple bar to begin with.

And the calculation is made to check which load the fixed joint must withstand for the elevator's own weight.

I intend to present it in steps so if I got something wrong I can adjust it before the next step.
If it's okay with you people?

Best regards Anna

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[LittleInch]

It's this bit of data which is my supposition, but it may be something to do with the pressure in the cabin.

however it seems something happened between 12 and 18 seconds after the initial drop in altitude that started to reduce vertical speed and level off the dive. But then either G force / velocity ripped the wing off or the pilot blacked out. Maybe. But it's all there is to show that at that point something was happening to change the rate of descent.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Alistair_Heaton]

you would get quite large pressure changes when the door opens or shuts.

A plane free falling descends slower than when powered I am sure you have seen pics of freefall jumps where they get back into the jump aircraft.

 

[RedSnake]

Looking at the report and those direction traces you posted there is something not matching in terms of the time traces compared to the accident report. Also I think fight radar data if they don't get a new reading it just repeats the same one. You're better off plotting the co ordinates and then working out the heading rather than using the heading data I think.

Yes I guess you are right, if you can't do it for me ;-) I can allways try flashing my eyelashes and say pleace, sometimes it works you seems to have already done it.
I am just trying to get a correct speed from MIL radar data.

The pilot is maintaining a pretty steady speed and altitude at an air speed of around 80 knots based on a 30 knot head wind which he was more or less heading into. Then he speeds up a bit to about 87 kts but stays level, Then the speed dies, but the altitude hardly changes.

Yes and it is that part before, that I would like recalculate the speeds for ??

One thing to consider is whether as the speed increased a bit did this make the door more difficult to open and so the pilot got a call to slow down a bit "so that I can open the door"

I am quit shore that no call to the pilot with requests was made. That is not there rutin. And I have seen many jump films and never seen that happen.
They look at the GPS to se where they are and then wait until the propeller speeds is 2000 rpm and it was never under 2350 rpm in motordata or in the soundfile.
And the ruels was also changed one and a half mounth earlier that the door was not to be force opened.
Because the lever inside the door that holds it looked closed and open hade broken because of bad welding and my partner hade to keep the door cloesed while they where going down for landing.
It was a colleague of mine that welded it togheter again, he is the only one we have who is a licensed welder.

That is not and with the extra weight at the back with everyone starting to shuffle around to get ready to exit he powered back too much and couldn't hold the aircraft level??

This lift was not going to be a formation jump as I have understod it, they where planing on jumping out two and two. But I can ask.
And i have a film from a formation jump where ju can see quit good how it is done. Unfortanatly it is not on the net so I can't show you. I am not shore what your definision of shuffle is?
There is this film but I think that they only are six or seven in the plane so it isn't really the same.

https://www.youtube.com/watch?v=VbOowIsOKZ4

Looking at the report and those direction traces you posted there is something not matching in terms of the time traces compared to the accident report.
True they are from flieght24 I got them myself. I have never asked for the ones that SHK claims to be more correct the ones from the airport transponder system see (thread 2 Dec 20 20:04)

Also I think fight radar data if they don't get a new reading it just repeats the same one.
True

You're better off plotting the co ordinates and then working out the heading rather than using the heading data I think.
Just trying to calculate the correct speed.

One think struck me when looking at the radar trace on figure 18 of the report.
The pilot is maintaining a pretty steady speed and altitude at an air speed of around 80 knots based on a 30 knot head wind which he was more or less heading into.
Then he speeds up a bit to about 87 kts but stays level,
Then the speed dies, but the altitude hardly changes.
Until he gets below stall speed and then banks and turns left and falls down 200m in 4 seconds and a further 200m in the next 4 seconds.
That is wy I want to know the correct speed.

Now why is the crucial question here that we don't have any major clues to.
One thing to consider is whether as the speed increased a bit did this make the door more difficult to open and so the pilot got a call to slow down a bit "so that I can open the door" and with the extra weight at the back with everyone starting to shuffle around to get ready to exit he powered back too much and couldn't hold the aircraft level??
That is the SHK:s picture, se mine abow.

With 30 seconds to go the jumpers will have wanted the door open so they could start to peer out and see if they can see the ground .

The door is not opened more then 10 seconds before jump.

It's interesting that the official protocol is no jump if you can't see the ground, but was that enforced when you have good GPS??
You could se the ground at the airport where the jump should be made even with surronding clouds, it is apparently a common phenomena at the airport..

When the wind is blowing from that direction 351-352 it is a some hight diffrence in the the terrain on the east side of the river not on west side so clouds bild up there but wind coming from the sea can come in on top of the river and makes it clearer on the airport side where it is almost just flat fields around.
(And now I am really guessing!)

Skydivers want to jump out of planes. Even in the middle of a cloud. They really really don't like going down in a plane and having to get out lower or worse still land. The centre has to refund the jump money or doubles the money spent the next time. Most centres operate on thin if any margins so the pilot was probably feeling a bit of time pressure as he had had to hang around waiting for final clearance. All the time you're burning fuel you haven't been paid for.

This is a member association of people who have jumped together some for more than 30 years, they would not consciously take risks to make money. It might have been the pilot trying to impress or do what he thougt was requred.

Best regards Anna


“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[RedSnake]

Funny enough it was very easy to teach engineers how to physically fly the machine but a rather large number struggled with navigation.

I think that this is something that might belong to the hobby forum.

https://www.eng-tips.com/viewthread.cfm?qid=476779

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[RedSnake]

Okey new question?
12:06:14 Ground speed =98,35*0,539957=53 knot flight direction 330 deg MIL radardata
Is it heading or course that should be 330 ??

Best regards Anna

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[LittleInch]

Heading is the direction the airplane is pointing.

Course is the course over the ground.

So the radar plots course because it has no real information on aircraft heading and doesn't really care which direction the plane is pointing.

So 330 is course.

Heading in this case will be higher because the head wind is coming from the right

That video is interesting.
They take 30 seconds from opening the door to getting out.
There are 5 of them all out at the same time.
They can all kind of stand up / crouch and will by sheer nature tend to move backwards and bunch up a bit.
If the lift was a set of two people x 4 then they would probably want to start getting the first two out a bit early so the last pair don't end up in the forest.
Standing / crouching / kneeling makes the whole mass of the aircraft unstable and it's very easy to fall back wards / forwards/ sideways compared to sitting down.

But we just don't know why you get this sudden reduction in ground speed and hence air speed with no apparent loss of altitude for those crucial 8 to 10 seconds before the turn / roll and dive into the clouds. I was just being hypothetical about a possible reason why the pilot would throttle back.

This site has some good photos of the plane

https://www.flyingmag.com/photo-gallery/photos/ga8-airvan-photos/

Now I don't know a whole heap about which lever really does what in terms of varying the prop speed, but could the pilot have chosen the wrong lever? And pushed pitch forward instead of throttle or vice versa? Just asking as he was preparing to reduce prop speed etc to start the main run in and let the door be opened.

I've seen jump aircraft before, even smaller ones like this where there are marked lines in the cabin and big warning signs about "No more than X jumpers beyond the Red line" and also "If X jumpers are beyond the red line then no more than Y jumpers between the red line and the green line (line further towards the front of the aircraft). I don't see that sort of information on the cabin floor of this aircraft.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[RedSnake]

So 330 is course Thank you I thought it was but I was not sure.

Heading in this case will be higher because the head wind is coming from the right ??? I would say left??

They take 30 seconds from opening the door to getting out.
True but this was really good weather conditions.
In the film I have it is exactly to the point 10 second from door opening to jump.
And of course, it differs from different jumps depending on who is on the plane and what they intend to do.
In this film, there are only very experienced jumpers.
The day of the accident it was quite cold up there so, my opinion is that they would not fly with the door open more than absolutly was necessary. Even though the cabin is air heated.

But we just don't know why you get this sudden reduction in ground speed and hence air speed with no apparent loss of altitude for those crucial 8 to 10 seconds before the turn / roll
What annoys me is that at that exact location 12:06:53 there are also disturbances on the primary radar.
But SHK says that they are registered about 33 seconds after the plane has passed that point.
I do not know what height the registrations have or how large objects the radar can perceive?
But if it had been an optimal freefall of something without more information, it is not excluded that it was something from the plane.

And pushed pitch forward instead of throttle or vice versa?
Everything is possible.
But they have such a different design, I guess it is because you should also be able to feel that you are on the right lever.
And I have not come as far with the wastgate as they have also had problems with before, which had not been fixed.
or this
The following forecasts were issued for Umeå Airport:
TAF ESNU 140830Z 1409/1418 16006KT CAVOK PROB40 1411/1417 BKN045TCU =
TAF ESNU 141130Z 1412/1421 16006KT CAVOK PROB40 1412/1417 SCT045CB =
The forecasts show a high probability of drying clouds during the period after kl. 13.00 local time and cumulonimbus activity after kl. 14.00.


I don't see that sort of information on the cabin floor of this aircraft.
No that was not a requirement.
from the report.

2.6.3 The flight manual and the certification
The flight manual and accompanying supplement do not provide clear directives for how the mass center position is to be calculated when lifting parachutists, but only state that they are to be distributed evenly over the cabin floor. The only thing that in any way describes the parachutists' movements in connection with door opening and exit is that there may only be five jumpers behind an imaginary line across the aircraft in the front edge of the cabin door, of which a maximum of three outside the aircraft, and that the jumpers must be informed not to gather far behind for a longer period of time

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[RedSnake]

A question to Alistair or someone who flies "real" aircrafts.
When you arrive for landing at an airport, what determines which direction you enter the runway?

Best Regards Anna

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[Alistair_Heaton]

Which way the wind is blowing usually we want a head wind. But we may take a tail for operational reasons.

 

[RedSnake]

Thanks
Head wind? Against the wind ??
What height would you be at about 2 km, 6600 feet before landing?

Best Regards Anna

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[Alistair_Heaton]

wind is blowing at the nose of the aircraft so the ground speed is decreased.

we deal with nautical miles which i s 1 second of arc at the equator which is 6080 ft. And then use a 1 in 60 rule ie 1 degree is 1 ft and 60 ft or 1m at 60 meters it makes mental arithmetic easy.

At 4 miles with 3 deg glide we would be at 1200 feet above touchdown. 7000ft I would need about 16 Nautical miles in a commercial aircraft and about 8 miles in a single engine piston.

Right I started work 12 hours ago at 3 am and just got in so going to bed for a couple of hours.

 

[RedSnake]

Okey, sleep tight ..happy dreams..
/A


“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[LittleInch]

BTWE that picture of the controls is from the GA-8. But yes, they make the levers different so you should be able to do it by feel without looking and I think (please correct me any pilot) that they are always in the same order, a bit like clutch, brake, accelerator on cars. So it's unlikely, but if the pilot was suffering from lack of O2 and just made an error?

I don't really know how you change the RPM of a fixed speed prop but assume it's one of the other levers or dials?

But then the engine data records don't show any sudden decrease of speed or manifold pressure in the final seconds of recording. In fact the last recording is more power / speed until it apparently gets cut off when the no 1 bus is cut out.

So why the sudden reduction in apparent airspeed?

Was this really a sudden increase in wind speed? Can things like that happen just above a cloud?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[RedSnake]

but if the pilot was suffering from lack of O2 and just made an error?
I can think of a couple of other misstakes he could have made much easier.

I don't really know how you change the RPM of a fixed speed prop but assume it's one of the other levers or dials?
It is the blue one.

But then the engine data records don't show any sudden decrease of speed or manifold pressure in the final seconds of recording. In fact the last recording is more power / speed until it apparently gets cut off when the no 1 bus is cut out.
What I am a bit uncertain about is if the the continued rice in inHG after the last climb of 200m(655 feet) is normal, it should return to it's normal value when the plane stopps climbing but how long that normaly takes I do not know or if he was making changes to the fuel mixture.

So why the sudden reduction in apparent airspeed?
I have some ideas, but I wait a bit with them, it takes such a long time to write when so many questions are to be dealt with at the same time. ;-)
Remember that English is not my first language so it takes a little longer for me to write down the answers

Was this really a sudden increase in wind speed? Can things like that happen just above a cloud?

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[RedSnake]

I have an idea that can be speculated on, it contains strange radar data tracks. Maybe it could be a thread of its own?

Best regards Anna

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[Alistair_Heaton]

Drag changes with AoA so a increase change will cause the aircraft to slow which will increase drag which might have been the reason why he increased the prop RPM because power is the torque x rpm.

Yes its the middle lever and will be a cross shape, mixture is on the right and is always a multi point star shape.

 

[moon161]

Alistair, is the straight line power curve for the jet based on constant static thrust? I was scratching my head about that for a minute or three.

 

[LittleInch]

So if the pilot is actively maintaining level flight by positive nose down on the control column then for whatever reason lets that positive force reduce, you'll stall the plane but without really showing any increase in altitude?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Alistair_Heaton]

That's a pure jet with no bypass "line" sort of jet that was on the 737 classics or DC10 etc. Its a cowled ducted compressor which is spinning extremely fast which means as the speed increases there isn't any real change in the angle of attack of the front blades. The fast you go the more air goes in the front and the more thrust it will develop.

With a prop the speeds are limited due to the prop tips going transonic and as the speed goes up the angle of attack of the blade changes and the amount of thrust goes down. Which is the reason why they use constant speed adjustable pitch props the prop speed is kept below transonic issues and the blade angle is change to allow more power to be imparted to the airflow.

 

[Alistair_Heaton]

You would trim the aircraft so you weren't holding any force on the control. If the CoG suddenly went rearwards you the AoA would increase drag would increase and you would slow down. Your height might not change that much for a few seconds. But this flying on the dirty side of the drag curve as we call it is a pain in the bum and if you slow down you need more power to maintain speed and if you are already at max the only energy source left to get you out of the hole is to descend. Just before it stalls you may need 70-80% of full power to maintain speed at straight and level where as at Vy you would need about 40%