Piper crop spraying type crash in Mexico.
Thread Starter
Piper crop spraying type crash in Mexico.
Structural failure during a pull-up:
https://x.com/ondisasters/status/169...2uPorHJJ31eXTw
Pilot did not survive the crash.
See also: https://aviation-safety.net/wikibase/345178
https://x.com/ondisasters/status/169...2uPorHJJ31eXTw
Pilot did not survive the crash.
See also: https://aviation-safety.net/wikibase/345178
Last edited by Jhieminga; 3rd Sep 2023 at 14:01. Reason: Added Aviation-Safety.net link.
That was pretty horrible. I know nothing of Mexican aviation, but I wonder if the wing spar attach AD was complied with, or if one of the STC fixes was installed.
That wasn't crop spraying in any shape or form but some stunt for a wedding or similar occasion.
Doesn't change the end result but possibly did ask too much of the aircraft 🤔
Doesn't change the end result but possibly did ask too much of the aircraft 🤔
Thread Starter
Didn’t mean to imply that it was spraying crops. I just couldn’t figure out the type from the video and thought ‘Piper crop spraying type’ to be a decent approximation. The interesting question is whether the manoeuvre was less severe, similar or more severe than during normal spraying ops.
The result is, of course, tragic and traumatic.
But if I've got this right, and I don't care how well they've cleaned it, they are using pesticide-delivery equipment to spray vapour onto the participants at a family event which includes a pregnant woman.
But if I've got this right, and I don't care how well they've cleaned it, they are using pesticide-delivery equipment to spray vapour onto the participants at a family event which includes a pregnant woman.
What's a little pesticide amongst friends
GA fatal accident during Mexican family gender reveal party
Pilot is climbing at the same time as operating the hopper dump facility. Not a problem for a 'sound' machine, but these aircraft have been doing this for years when spraying, and there are numerous 'AD's' for struts, centre cluster. wing fittings, that need to be kept up. In actual fact the 'dump' reduces the actual load instantly which could mean an increase in the climb rate. In normal spraying ops the load is gradually reduced over several runs although some 'spirited' turns are frequently seen between runs. The combination of a high lift wing. plenty of power, and the ability (if wished) to instantly reduce load could easily lead to an overstress situation, and the wings are load lifters but not for abrupt manoeuvres.
Pilot is climbing at the same time as operating the hopper dump facility. Not a problem for a 'sound' machine, but these aircraft have been doing this for years when spraying, and there are numerous 'AD's' for struts, centre cluster. wing fittings, that need to be kept up. In actual fact the 'dump' reduces the actual load instantly which could mean an increase in the climb rate. In normal spraying ops the load is gradually reduced over several runs although some 'spirited' turns are frequently seen between runs. The combination of a high lift wing. plenty of power, and the ability (if wished) to instantly reduce load could easily lead to an overstress situation, and the wings are load lifters but not for abrupt manoeuvres.
And the party-goers mostly don't hear the wing go above their cheers, and the crump of the impact is a couple of hundred yards behind them.
Join Date: Nov 2006
Location: Down south
Age: 68
Posts: 339
Likes: 0
Received 0 Likes
on
0 Posts
An energetic pullup after a high speed pass (Probably at VNE) produces high loads that may well exceed the structural strenght of the longeron. Hence the failure. I would reckon this pullup would be in the 4G's + range, and may not have been the first one with this aircraft.
Pobjoy has never 'sprayed' with his PA25 (235) but the machine is a great Banner & glider tower. In fact the 'pull up' for a banner launch is not needed for spraying other than to avoid obstacles around fields. Glider launching is airframe friendly but the engine requires careful use on the descent to avoid shock cooling, and of course both operations are not carrying a hopper load which means you are well below max weight.
The top struts/fittings on a Pawnee are very important and subject to some fairly strict inspections but the basic wing is a lift junkie not an aerobatic tool. If you happen to be pulling some G and dump at the same time it is probably going to increase the G very quickly and 'possibly' the wings outboard of the struts will be taking the extra strain. A stripped out PA 25 without the spray equipment is an express lift and of course has no large fuel load, so the elevator input should be careful.
The top struts/fittings on a Pawnee are very important and subject to some fairly strict inspections but the basic wing is a lift junkie not an aerobatic tool. If you happen to be pulling some G and dump at the same time it is probably going to increase the G very quickly and 'possibly' the wings outboard of the struts will be taking the extra strain. A stripped out PA 25 without the spray equipment is an express lift and of course has no large fuel load, so the elevator input should be careful.
It makes zero sense for the structural loads to go up when the load is dropped. The angle of attack will momentarily be the same, lift will be the same, and the aircraft will rise. As you get more vertical speed the relative wind effectively reduces angle of attack and also you have less weight.
A force-body diagram would be a good means to understand the forces.
A force-body diagram would be a good means to understand the forces.
On the face of it I would agree with IFMU, but this would seem to be contradicted by (I think) at least 2 C-130 fire-bombers which have suffered similar wing/fuselage separation immediately following payload-release. Could it be a shift of CG causing an exagerated response to pilot's pitch-up input?
With the aircraft suddenly climbing, would the reduced angle of attack on the horizontal stabilizer due to the change in relative wind tend to pitch the nose up (if not countered)?
Thread Starter
Just a little theory exercise: Your G is nothing more than L/w, which means that by decreasing w, we're also increasing G if the rest stays the same. I don't know how much weight is in a full hopper (relative to total weight of the aircraft) but dumping half your weight would effectively put 2G on the airframe. If you also initiate a pull-up, you need to add that to the Gs already there from the dump. This is based on everything else staying the same though... so keep in mind that the aircraft rising, airflow changing etc will have an influence too.
