20 replies to this topic

[rotorwashed]

[akscott60]

Yea, someone put that in the military forum. That video has spread like wildfire on all the websites I do to.

Yea, I really doubt those two guys/gals are ever going to be allowed to fly again.

[rotor91]

Some are saying DA was a major factor. And yes, probably not going to see a cockpit anytime soon!

[ADRidge]

That'll ruin your day!

[Pohi]

Wow.

I can't wait too see what they have to say about this on the other forums!

[SBuzzkill]

This made its way around the troop today. Ridiculously stupid.

[JCM5]

$20,000,000 of your tax dollars.

[Trans Lift]

Tut tut!

[RagMan]

Even that cyclic climb looked spongy! Don't think you're suppose to initiate a Return-To-Target manuever that low.... At least not under high DA and heavy weight.

[Helipilot PTK]

Not experienced in this maneuver (as you can tell by the helicopter I fly to the left), but I agree that that looked very shady from the start. Glad to here every one is alright.

[apiaguy]

that was awesome... I thought they were going to get away with just the hard landing/bonk on the snow... then things got real exciting!

[klas]

It sounded like the back wheel hit the top of the roof of the bldg when it made it 1st pass - am I hearing things?

[jim_222]

It sounded like the back wheel hit the top of the roof of the bldg when it made it 1st pass - am I hearing things?

No, something must have happened during the first pass, I think you are right. When i first saw it, I thought it was a wire strike, but the image is not very clear, to be able to tell

[JCM5]

It sounded like the back wheel hit the top of the roof of the bldg when it made it 1st pass - am I hearing things?

No, something must have happened during the first pass, I think you are right. When i first saw it, I thought it was a wire strike, but the image is not very clear, to be able to tell

I don't think so. At that speed, there would be visible damage to the tail section if it struck the roof.

DA is more than likely a huge factor here. Trying to show off for his buddies and mis-judged the RTT maneuver. Nearly killed a few soldiers on the ground - you can see the tail rotor misses one guy by inches.

Just a pilot trying to be a cowboy.

[SBuzzkill]

Mushing

Mushing is a temporary stall condition that occurs in helicopters when rapid aft cyclic is applied at high forward airspeeds. Normally associated with dive recoveries, which result in a significant loss of altitude, this phenomenon can also occur in a steep turn that will result in an increased turn radius. Mushing results during high g maneuvers when at high forward airspeeds aft cyclic is abruptly applied. This results in a change in the airflow pattern on the rotor exacerbated by total lift area reduction as a result of rotor disc coning. Instead of an induced flow down through the rotor system, an up flow is introduced which results in a stall condition on portions of the entire rotor system. While this is a temporary condition (because in due time the up flow will dissipate and the stall will abate), the situation may become critical during low altitude recoveries or when maneuvering engagements require precise, tight turning radii. High aircraft gross weight and high density altitude are conditions that are conducive to, and can aggravate mushing.

Mushing can be recognized by the fact that the aircraft fails to respond immediately, but continues on the same flight path as before the application of aft cyclic. Slight feedback and mushiness may be felt in the controls. When mushing occurs, the tendency is to pull more aft cyclic which will prolong the stall and increase recovery times. The cyclic must be moved forward from the position that caused the mushing condition in order to recover once mushing
occurs. This reduces the induced flow, improves the resultant angle of attack, and reduces rotor disc coning which increases the total lift area of the disc. The pilot will immediately feel a change in direction of the aircraft and increased forward momentum as the cyclic is moved forward.

To avoid mushing in future situations, the pilot must avoid abrupt inputs but instead smoothly and progressively apply aft cyclic during high g maneuvers such as dive recoveries and tight turns.

Dig In

While making large aft cyclic movements, the pilot should be aware of the helicopter’s tendency to rapidly and unpredictably build g-forces. As the cyclic is moved aft, the rotor disk responds by tilting aft, which tilts the thrust vector aft and ultimately causes the aircraft to pitch nose-up. This rapid pitch-up also increases the length of the aircraft thrust vector, which will in-turn increase the pitch-up rate. The rapid onset of the pitch-up motion due to the tilting and then lengthening of the thrust vector is considered destabilizing and is countered by the helicopter’s horizontal tail or stabilizer, which will try to drive the nose back down. For large pitch-up rates, the tendency of the main rotor to continue pitching-up will overpower the horizontal tail/stabilizer and the aircraft will “dig-in” and slow down rapidly. Dig-in will usually be accompanied by airframe vibration and sometimes control feedback.

Aft cyclic movements will give predictable increases in g-load up to the dig-in point; however, the dig-in occurs at different g-levels for each model of helicopter. The point at which dig-in occurs depends on a number of factors, but most important is the size of the horizontal tail/stabilizer and the amount of rotor offset. For most helicopters, this point is between 1.5 and 2.0 g. Pilots should be prepared for dig-in during aggressive aft cyclic inputs, especially during break turns.

Edited by SBuzzkill, 23 March 2012 - 18:53.

[SBuzzkill]

[akscott60]

Well Buzz, we already know the 58 does them sexy

[lelebebbel]

Mushing is a temporary stall condition

Interesting, I didn't know there was a name for it. More than a few crop-dusting helicopters have been lost this way..

Another video that shows "Mushing" with very unfortunate consequences here (MD500 loop attempt). Warning, this was a fatal accident, don't click if you don't want to see this.

http://www.nycaviation.com/2010/08/video-helicopter-crashes-in-competition-during-loop-de-loop-attempt/




Serious question about that Apache accident:
Why is the moveable horizontal stabiliser pointing down in this picture? Shouldn't it be pointing up, given that the pilot most likely has the cyclic pulled all the way back?

[Pogue]

Serious question about that Apache accident:
Why is the moveable horizontal stabiliser pointing down in this picture? Shouldn't it be pointing up, given that the pilot most likely has the cyclic pulled all the way back?

Assuming it's like the Blackhawk, the stabilator is programmed off of airspeed with the intent of keeping the airframe attitude (mostly) level. At slow speeds it moves down to lift the tail. It's not controlled by flight control position.

[lelebebbel]

Thanks. Looks like it worked as advertised then.