I did some full down Autos

[betr_thn_Icarus]

So I have done a few full down autos. After all of the hype I thought there would be some amazing personal breakthrough after realizing I could do them. It was very anti-climatic. Really I just was a little glad to see they are nothing more than a very very short run on landing at the end of a normal auto. If you don't get the chance to practice them just know that if you are going to a hover without problems you are in the clear and there really isn't that much more to be had from a full down. On the other hand if you have the chance then do it just for your own realization that it isn't that big of a deal.

 

Just my thoughts, keep in mind I am still just a student.

 

How does everyone else feel? What was your first one like?

[Chuck Potts]

I did them in a TH-55 when I was working on my CFI. It was some of the most exciting flying I have ever done! Shortly thereafter one of the working CFIs that had thousands of hours and loved doing full touch down autos crashed doing one. I have shied away from them ever since. I should go out and try them again as mostly what I fly these days is a 300C and that is a much more forgiving machine than the TH-55.

Your Friend, "The Hoverbug"

[permison]

So I have done a few full down autos. After all of the hype I thought there would be some amazing personal breakthrough after realizing I could do them. It was very anti-climatic. Really I just was a little glad to see they are nothing more than a very very short run on landing at the end of a normal auto. If you don't get the chance to practice them just know that if you are going to a hover without problems you are in the clear and there really isn't that much more to be had from a full down. On the other hand if you have the chance then do it just for your own realization that it isn't that big of a deal.

 

Just my thoughts, keep in mind I am still just a student.

 

How does everyone else feel? What was your first one like?

 

I have this debate all the time. I truly believe full downs should be taught as part of the standard. In the Army we had a saying "Fight like you train, train like you fight". This means when you get in a real situation requiring an auto all the way to the ground then you are fully prepared for it. If your first full down is only in a real emergency then you will question yourself all the way to the ground. I think the idea of teaching emergency proceedures to 8/10s of completion is a mistake and pilots will fly to a hover, try to recover and then not have enough to get the aircraft safe on the ground. Which results in a hard landing if they are lucky, and a balled up ship if its not their day. I don't believe a safe hover recovery proceedure will help when you have the real one as it leads most pilots to plan to land when they are still 5 feet in the air. The change from a standard auto to a hover auto in one motion is very difficult but is what is being taught.

 

Full downs are hard and dangerous (mainly due to it not being practiced) but practice will lead to better performance and safer pilots in emergencies. I don't expect this post to change anyones minds but had to add my two cents as I strongly disagree with this practice.

Permison

[Linc]

I did them in a TH-55 when I was working on my CFI. It was some of the most exciting flying I have ever done! Shortly thereafter one of the working CFIs that had thousands of hours and loved doing full touch down autos crashed doing one. I have shied away from them ever since. I should go out and try them again as mostly what I fly these days is a 300C and that is a much more forgiving machine than the TH-55.

Your Friend, "The Hoverbug"

From what I understand, there are no significant dynamic component differences from the Hughes TH-55 (Hughes Model 269A) and the Schweizer 300C (Hughes Model 269C) except for the engine. Granted, I don't have a lot of any experience with or knowledge of the differences, so...

 

What other differences are there that make the 300C more forgiving?

 

Thanks.

Edited January 22, 2007 by Linc

[jet trash]

From what I understand, there are no significant dynamic component differences from the Hughes TH-55 (Hughes Model 269A) and the Schweizer 300C (Hughes Model 269C) except for the engine. Granted, I don't have a lot of any experience with or knowledge of the differences, so...

 

What other differences are there that make the 300C more forgiving?

 

Thanks.

 

The primary differences of the TH55 and the 300C.

 

The TH55 main rotor blades are 1 foot shorter than the 300C (1190 blades vs 1185's on the C)

 

The mast on the TH55 is shorter than the 300C's.

 

The tailboom on the TH55 is a foot shorter than the 300C.

 

The TH55 is 180hp (five minute limit) 160hp normal, the 300C is 220hp derated to 190hp.

 

The TH55 operates at 2700 rpm, and the 300C operates at 3200rpm.

[apiaguy]

The primary differences of the TH55 and the 300C.

 

 

"The TH55 main rotor blades are 1 foot shorter than the 300C (1190 blades vs 1185's on the C)"

9 1/4 inches shorter

 

"The mast on the TH55 is shorter than the 300C's."

Yes, 6 inches shorter on the Th-55 model

 

"The tailboom on the TH55 is a foot shorter than the 300C."

Yes, 11 1/2 inches difference

 

"The TH55 is 180hp (five minute limit) 160hp normal, the 300C is 220hp derated to 190hp."

220 hp would be an estimate, yes the C is derated for max manifold press. of 27.2 inches. that would correspond to 190 hp continuous. The interesting thing here is that the TH-55 is a normal 180hp parallel valve engine that makes 180 hp at 2700 rpm. So if the engine is spinning 2900 rpm how much power is it making at 30 inches manifold (assuming you could pull that). Now accounting for losses in the exhaust, mags, etc.. maybe it is making a "true" 180 hp. The C model D1A engine is an interesting engine because it "guarantees" the hp it claims unlike most all engines..... The only other engines I can think of off hand that "Guarantee" their power ratings are the Continental 550 engines.

 

"The TH55 operates at 2700 rpm, and the 300C operates at 3200rpm."

The TH55 operates at 2700 to 2900 rpm and the C 3000 to 3200 rpm

 

The C model tail rotor diameter is 5 inches greater than the TH-55

 

 

 

Now the question is do these two aircraft have any handling difference? My experience is yes and no. Yes the C has more power, but it depends on how you load the aircraft. Both aircraft at gross weight there is no real performance difference. The C has a greater useful load so lightly loaded it will outperform the 55 at a typical mission weight. The autorotational characteristics of the aircraft can only be summed up as nearly identical. Do the dynamic components listed above really change the flight characteristics. I don't think so. The 55 is a lighter aircraft and responds better (some might say more twitchy) I think the differences IMHO can best be summed up by how the aircraft is going to be flown (weight) better than by what the dynamic components are.

Edited January 22, 2007 by apiaguy

[Guest pokey]

they fly pretty much the same, notable difference:

 

the A,B,TH-55 need more left pedal upon take-off & hover, also it "squats" on its dampers more than the C,--- so you can really "feel" it off the ground B4 it actually lifts off.

 

As far as performance goes? I've flown my B on the same days as i have flown a C with the same weight & both of us decided that my B was more powerful. I've also flown some really "healthy" A's (TH-55's).

[jet trash]

they fly pretty much the same, notable difference:

 

the A,B,TH-55 need more left pedal upon take-off & hover, also it "squats" on its dampers more than the C,--- so you can really "feel" it off the ground B4 it actually lifts off.

 

As far as performance goes? I've flown my B on the same days as i have flown a C with the same weight & both of us decided that my B was more powerful. I've also flown some really "healthy" A's (TH-55's).

 

same here. it seems they all (A,B,C's) have their different personalities. i had a TH55 that was very powerful in the engine dept, and also did auto's very nicely.

[jehh]

I have this debate all the time. I truly believe full downs should be taught as part of the standard. In the Army we had a saying "Fight like you train, train like you fight".

 

And if you go join the Army, that is how they will teach you...

 

However, in the real world, where we have to make a buck doing this, full down autos just don't make any sense from the flight schools point of view.

 

They are hard on the equipment, increase the risk of training accidents, and don't provide that much better training to offset those issues.

 

My 2 cents...

[permison]

And if you go join the Army, that is how they will teach you...

 

However, in the real world, where we have to make a buck doing this, full down autos just don't make any sense from the flight schools point of view.

 

They are hard on the equipment, increase the risk of training accidents, and don't provide that much better training to offset those issues.

 

My 2 cents...

 

Can't dispute the abuse to the equipment and the greater risk. I think teaching pilots to not follow through to the end is a mistake but I agree with your points. Wish there was a different way to teach though. Figure that out and it's worth a lot more than 2 cents. I wonder if there is a study out there which shows that pilots taught full downs opposed to hover recoveries had better outcomes (or vis-a-versa) ;-)

[Linc]

Tonight I was glad it was SEFs and not full autos. The aircraft was not rigged for autorotation in the conditions. There were no indications that this was the case until you entered with a rapid drop off of rotor rpm. I could get it to come back but not to 100%, even with a decel to try and spool it up. We brought the throttle back up to full and continued the maneuver.

 

If it had been touchdown autos, we'd have balled it up, since I couldn't get it to bite into a decel until 15-20 degrees nose high. By then, it just accelerated the descent, since there was no brake state, and I had to level and start pulling the torque in at 50 feet to keep from planting it into the runway.

 

We turned the aircraft back in to maintenance.

Edited January 23, 2007 by Linc

[mechanic]

I don't think so. The 55 is a lighter aircraft and responds better (some might say more twitchy) I think the differences IMHO can best be summed up by how the aircraft is going to be flown (weight) better than by what the dynamic components are.

 

But, isn't the VNe slower on a TH55 vs. C? Do you think the TH55 is inbetween a 2 bladed sys and C, in rotor response time? On the power note, I was thinking the Type Cert listed upgrade engines and parts for each, allowing the use of newer more powerfull engines on the older airframes, correct?

 

 

 

Later

[apiaguy]

But, isn't the VNe slower on a TH55 vs. C? Do you think the TH55 is inbetween a 2 bladed sys and C, in rotor response time? On the power note, I was thinking the Type Cert listed upgrade engines and parts for each, allowing the use of newer more powerfull engines on the older airframes, correct?

Later

 

Sorry for hijacking this thread off of touchdown autos to comparative analysis of the Hughes/Schweizer performance characteristics for those reading.

 

Yes the VNE is slower on the A/TH-55 and B model (75 KTS vs 95 in the C). Some of this is due to the earlier models having thinner canopy glass on the windshields (all aircraft can have the thicker stuff now) and some of this is due to the main rotor RPM which is higher in the earlier models. The C model was an attempt by Hughes to expand the earlier model characteristics.... specifically the low VNE, and increase usefull load (always gotta have more speed and carry more weight)

I don't know how many people have tried to cruise at 95 kts in a C model but it ain't easy (nearly impossible) It just doesn't want to do it and the flight attitude is aggressive to say the least. The earlier models will easily cruise at VNE a couple inches manifold above hover power. I have personally flown the early models to 85 kts with no abnormal vibrations, no droop stop pounding or other problems. I had one guy tell me he did 112 MPH in a TH-55, I wouldn't try it, but It would probabally do it on the edge to say the least.

The point is the early airframe is the same as the current design and while there have been some changes and expanding of the envelope, I believe some of the design limits on the early models is due to Hughes abandoning them when they developed the C. It is just too much paperwork nightmare to change the TCDS to incorporate progression and the company wants you to buy a new one. Whew, that was a mouthfull.

 

The Type Certificate only allows upgrades to the original A model in that it allows the use of the HIO-360-B1A engine instead of the earlier O-360-C2D originally typed in the design. Later the C2D was eligible for conversion to an HO version but the HIO engine is what is preferred. There is an STC for installation of the angle valve HIO-360-A1A engine for installation in the A model (that engine comes standard in the B model)

 

I'm not sure what you meant on rotor response time, both TH-55 and the C model are 3 bladed and would have faster response time than any 2 bladed system. I would have to guess the TH-55 would have the fastest response time due to rotor RPM. But from the pilot seat they are the same (at least my senses can't tell the difference).

Edited January 23, 2007 by apiaguy

[Pogue]

Tonight I was glad it was SEFs and not full autos. The aircraft was not rigged for autorotation in the conditions.

Linc,

 

Could you elaborate on that? The thought of flying an aircraft that needs to be rigged specifically for autos just scares the hell out of me. Is this an actual rigging or setup problem or a low gross wieght issue. I know Robbies won't recover to 100% in the glide if they're light (not a problem I normally have...) but that's not a mantenance issue.

[Linc]

Pogue,

 

It is a pitch change tube/link setting that sets the angle of attack to ensure the rotor achieves 100% RRPM (+/- an RPM range) during autorotation. This setting can change in areas where weather changes are significant between seasons. Up here in the North, we have warm summers and cold winters which makes for a significant change in DA. We normally try to have it set during the moderate seasons, so that it usually good enough throughout the year.

 

I think it is a military requirement, or at least a requirement on this aircraft, to verify it twice a year.

[Pogue]

Interesting - Why not just set it so it could overspeed to something like 110% and then control RRPM with the collective? Or would that negatively impact the full pitch setting? I'm assuming that you can pull more pitch that the engine has power...

[Linc]

I think that is part of the issue. I'll have to talk with our senior maintenance pilot to find out. I'm assuming that it would end up being something on the opposite end, being too close to the high end that you would continually run the risk of the rotor just spinning itself off the mast.

[Eric Hunt]

The problem with having auto revs set too high (apart from screwing it off the mast) is having to carry too much collective to control them. At the bottom of the auto, there isn't much left to cushion on.

 

In the real event, you would lower the lever towards the end of the descent and let the revs build up - wouldn't matter if you overspeed the head, you are already having an emergency. But for training, you don't want to damage the bird, and carrying collective into a touchdown is relying too much on good judgment.

 

In New Guinea, we took a Huey from sea level / 28 degrees C / 90% humidity, to 17,000' and then rolled off the throttle to demonstrate the effects of altitude on ROD and RRPM - the amount of collective needed was considerable. The flight envelope was something like a minimum speed for flight of 40 kt and a Vne of 60 kt - little margin for error. But this was 30 years ago and the numbers may have changed in my mind.

[mechanic]

I don't think so. The 55 is a lighter aircraft and responds better (some might say more twitchy) I think the differences IMHO can best be summed up by how the aircraft is going to be flown (weight) better than by what the dynamic components are.

 

I'm not sure what you meant on rotor response time, both TH-55 and the C model are 3 bladed and would have faster response time than any 2 bladed system. I would have to guess the TH-55 would have the fastest response time due to rotor RPM. But from the pilot seat they are the same (at least my senses can't tell the difference).

 

 

 

I took what you said to mean it was harder to handle than a C model, thats all.

[Linc]

The problem with having auto revs set too high (apart from screwing it off the mast) is having to carry too much collective to control them. At the bottom of the auto, there isn't much left to cushion on.

 

In the real event, you would lower the lever towards the end of the descent and let the revs build up - wouldn't matter if you overspeed the head, you are already having an emergency. But for training, you don't want to damage the bird, and carrying collective into a touchdown is relying too much on good judgment.

 

In New Guinea, we took a Huey from sea level / 28 degrees C / 90% humidity, to 17,000' and then rolled off the throttle to demonstrate the effects of altitude on ROD and RRPM - the amount of collective needed was considerable. The flight envelope was something like a minimum speed for flight of 40 kt and a Vne of 60 kt - little margin for error. But this was 30 years ago and the numbers may have changed in my mind.

Eric,

 

Your last comment, I think, is illustrating the point accurately. We are at a negative DA this time of year (that night it was close to -2500' DA)

 

If the auto rpm is set at a positive DA (say +1500' DA), then at that setting's DA, the auto rpm builds to the correct range with the collective full down. Since, I can't lower the collective below full down, it seemed I couldn't reach that AoA for that negative DA in order to get the rotor up to the appropriate rpm. How I'm understanding it. I still have to talk to the maintenance pilot to make sure it is straight in my head.

[jehh]

Can't dispute the abuse to the equipment and the greater risk. I think teaching pilots to not follow through to the end is a mistake but I agree with your points. Wish there was a different way to teach though. Figure that out and it's worth a lot more than 2 cents. I wonder if there is a study out there which shows that pilots taught full downs opposed to hover recoveries had better outcomes (or vis-a-versa) ;-)

 

If we operated Jetrangers like the Army does, rather than R-22s and Schweizer's, I'd be fine doing full downs with students... Having done full downs in a 206, those are just non-events...

 

A full down in a R-22 is... an exciting experience...

 

For what it is worth, I agree that full downs would be better training, and if I wasn't paying the bills, I would probably post what you did.

 

Fly safe!