Training on grass

[aa777888]

Thank you, Gordy!

If grass is all you have then grass is all you have. But there's no reason to be going to grass if you have a choice. A little wear on the carbides isn't going to break anyone's bank. The old ways worked, but sometimes the new ways are an improvement. Just so long as your instructor or check pilot isn't letting you get away with improper technique, of course.

[Robbiee]

Originally Posted by Gordy

# 2 was a checkride for CFI demonstrating a touch down auto. The examiner had a rather large stomach and the student left it too late to flare and thereby attempted an aggressive flare but ran out of cyclic as it hit the instructors belly....they hit the ground fast and the skids "dug in"...

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This one is my favorite!

[Gordy]

Originally Posted by aa777888

Thank you, Gordy!

If grass is all you have then grass is all you have. But there's no reason to be going to grass if you have a choice. A little wear on the carbides isn't going to break anyone's bank. The old ways worked, but sometimes the new ways are an improvement. Just so long as your instructor or check pilot isn't letting you get away with improper technique, of course.

Don't get me wrong---I am definitely on the side of hard surface vs grass.....

Originally Posted by Robbiee

This one is my favorite!

Yep, unfortunately he has since passed on. This was a case of the student had learned "rote muscle movement" and did not fully comprehend the situation and adjust his technique.

The one in Pic A, had less than 25 hours on the airframe since new.........

These were the 3 airframes I showed Shawn Coyle when he visited back in 2005 right before he wrote his article on Touchdowns to hard surfaces.

[EvaDestruction]

If all the touchdowns are zero ground run, it makes no difference.

In the training environment, how many zero ground run autos are achieved? Very damn few unless they are all done into a 20 knot headwind.

[aa777888]

I have a copy of Shawn's "Little Book of Autorotations" There's a whole section on this subject.

[Hughes500]

Hm, got home after loads of touchdown auto's to grass. Haven't bent anything. Grass is much more forgiving to land on then a hard surface. As a comparison if I asked you to jump off a 10 ft wall would you wish to land on grass or a concrete surface ?

[Gordy]

Originally Posted by Hughes500

. As a comparison if I asked you to jump off a 10 ft wall would you wish to land on grass or a concrete surface ?

Bad analogy---your knees are designed to bend to absorb the impact with your feet firmly in one spot---skids are designed to spread which they may not be able to do if they dig into the grass.

And yes, I too have done 100's of autos to grass, but accept that the risk is greater than to a hard surface.

[megan]

There is absolutely nothing wrong with grass providing you have surveyed it prior to use to determine its suitability, we are talking training here, not when you've had a failure and few options. All our training was to grass and never had an issue in my seven years of military service, as said previously we used to even run on at 35 knots, no problem, because the surface was maintained. Fixed wing come to grief when landing on surfaces not suitable as well, even when they think it is - runway under repair, did you get the notam.




Gordy, the grass in your #1 and #2 photos would not have passed muster here as suitable for training, don't blame the grass, blame the standards of which you are willing to accept as suitable. Our system ensured a surface flat as a billiard table and the grass kept mown short.

[Robbiee]

Originally Posted by megan

,...Our system ensured a surface flat as a billiard table and the grass kept mown short.

Gee,..how realistic.

[Gordy]

Originally Posted by megan

Gordy, the grass in your #1 and #2 photos would not have passed muster here as suitable for training, don't blame the grass, blame the standards of which you are willing to accept as suitable.

I did not approve the grass...Like I said, I investigated the accidents and reported my findings.... I was not Chief Instructor or the person who approved training areas, hence I reported that the accidents "could possibly" have been prevented had the maneuvers been conducted to a hard surface..... That much is true .

[[email protected]]

Full TD autos can be conducted to grass safely but not all pilots possess the skills to do so.

So we are back to dumbing down training...........

[[email protected]]

Our system ensured a surface flat as a billiard table and the grass kept mown short.

I don't think anyone would describe the EOL areas at Ternhill, Shawbury, Middle Wallop and Culdrose like that (Brit Mil training areas) - and as for North Field at Netheravon with its downhill slope.....

[[email protected]]

#1 was a new instructor who was demonstrating having too much forward trim and allowing the helicopter to run onto the ground with forward motion...

# 2 was a checkride for CFI demonstrating a touch down auto. The examiner had a rather large stomach and the student left it too late to flare and thereby attempted an aggressive flare but ran out of cyclic as it hit the instructors belly....they hit the ground fast and the skids "dug in"...

# 3 Actually the third was a "flare" problem in that the instructor was not authorized to conduct touchdown autos and he did a "power recovery" to a hover auto and bounced forward pulling full aft cyclic---had he been to a hard surface, there is a good chance the skids would have spread a little and then skidded not compressed and then sprung up.

#1 - a very convincing demonstration by the instructor - too convincing
#2 - did he pass his CFI ride?
#3 - not authorised for touchdown autos and couldn't even get a power recovery right!

All three instructor errors and rather confirming a dilution of quality and ability in the instructor cadre......

[Gordy]

Originally Posted by [email protected]

#1 - a very convincing demonstration by the instructor - too convincing
#2 - did he pass his CFI ride?
#3 - not authorised for touchdown autos and couldn't even get a power recovery right!

All three instructor errors and rather confirming a dilution of quality and ability in the instructor cadre......

Like I said....I was not Chief Instructor...I just reported my findings and conclusions.

#1...Ironic huh....he was part of the MTP---Military Training Program, yep---former military pilots now in the civvie world teaching new military pilots...

#2... Nope he failed, was retrained and retested and I believe he passed on 2nd attempt

#3 See #1 above....I was the one who removed #3's authorization prior to this accident. He was subsequently 609'd (license revoked by the FAA and had to retest to get it back, which he never did).

[Hughes500]

Gordy not a bad one really as the grass and ground absorbs some of the shock as the aircraft touches down, hence you see indents in the ground. You can't seriously lell me that landing on a hard surface has less of a shock to the aircraft ? Of course the skids splay out as this is the first " crumple zone " the manufacturer puts in to protect us. The skids still start to splay on grass, you just dont get the harder shock especially when a student gets it wrong and one has to recover it

[aa777888]

Originally Posted by Hughes500

Gordy not a bad one really as the grass and ground absorbs some of the shock as the aircraft touches down, hence you see indents in the ground. You can't seriously lell me that landing on a hard surface has less of a shock to the aircraft ? Of course the skids splay out as this is the first " crumple zone " the manufacturer puts in to protect us. The skids still start to splay on grass, you just dont get the harder shock especially when a student gets it wrong and one has to recover it

I'm afraid you are totally missing the point, H500. It's not the vertical loads that are of concern. It is the horizontal component of the touchdown velocity that is of much greater importance. If there is any forward motion at touchdown and either a) the skids are not perfectly aligned and/or b) the turf is not perfectly smooth, this could result in a dynamic rollover. On pavement (asphalt, tarmac, whatever you call it in your neck of the woods) you can pretty much get away with murder since the surface is very smooth and level, with a coefficient of friction far below that of even a putting green. Sure, the grinding sounds are horrible. While those sounds, and the smell of burning carbide or metal, can be concerning, the reality is that the ability to slide safely is much, much greater than on grass. It is that which is important, not the vertical component.

Also, it's worth nothing that from a vertical perspective, it's not really that the grass is absorbing impact so much as that the grass surface is providing a different character to the ground effect as you touch down. Leaving aside any differences in ground effect from soft surfaces vs. hard surfaces, given the same vertical speed at impact a soft surface will keep the skids from spaying more so than on pavement, and this will transmit a higher shock load to the airframe.

The bottom line is that hard surfaces are safer. Period. Dot. Physics and all that sort of thing. Now if you want to argue that the additional safety margin afforded by hard surfaces is inconsequential certainly you are free to do so. But as Gordy has noted, there are far more touchdown auto related accidents on soft surfaces than on hard surfaces, regardless of how many you and others have survived unscathed. If you have hard surfaces available to you why would you not avail yourself of them to gain that extra margin of safety? Your instructor should be beating you about the head and shoulders for too much forward velocity, or vertical velocity, at touchdown regardless of what surface you have chosen. So choose the one with a more homogenous surface and a lower coefficient of friction, i.e. a hard surface, just in case things go a little sideways.

[Robbiee]

Get your heads out of the bubble wrap and just practice crashing to the type of surface on which you are most likely to crash.

[megan]

Like these folk Robbiee? Chose the runway rather than the grass, as if they had a choice, wonder what the result may have been if they came down on the grass.

You Tube

[[email protected]]

Also, it's worth nothing that from a vertical perspective, it's not really that the grass is absorbing impact so much as that the grass surface is not allowing the bubble of air underneath the helicopter to escape so readily. So it's an air cushion effect rather than a surface cushion effect. Indeed, leaving aside the air cushion, given the same vertical speed at impact a soft surface will keep the skids from spaying more so than on pavement, and this will transmit a higher shock load to the airframe.

You may have some valid arguments about using tarmac instead of grass aa777888, but that one is complete fiction. search back for Nick Lappos' destruction of the 'bubble of air' theory of ground effect.

Keep straight, don't chase the attitude with cyclic and don't lower the lever until you have stopped during the run on and it doesn't matter what surface or pretty much what speed you land on.

[meleagertoo]

Full TD autos can be conducted to grass safely but not all pilots possess the skills to do so.

Originally Posted by [email protected]

So we are back to dumbing down training...........

I am reassured to be reminded that the UK must posess one of the most skilful sets of helo pilots worldwide as every single one, civvy PPL and military, do all their EOLs to grass with no awareness that it was considered remarkable. (afaik)
You are, after all, practicing for emergency landngs in fields...