As I sit here at my computer I'm at +1G. If I looked at a G meter next to my computer it would be at rest. It is of course reading +1G. So not having a G meter in a helicopter what does a G meter read on the dial at rest, 1 or 0?
I've never thought about it.
Correction, a G meter in an aircraft will register 0-G's of acceleration (1G) when straight and level. Pulling either positive or negative G's will indicate (at least on the accelerometers I've used) the maximum number of G's pulled. http://www.aircraftspruce.com/catalog/i ... meters.php
I've done aerobatics using a G meter in a Great Lakes and Super Decathlon, and I was very surprised at how low the G meter registered compared to the amount of stick force I used. Conversely, a little "bump" on landing can register 3+G's quite easily, but it usually won't feel like it. YMMV
But since we're all just chewing the fat here, I'd like to address one thing that George said regarding the rudder on a 170 not being capable of initializing a snap roll at manuevering speeds. I maintain that if you have enough rudder to spin (which doesn't take much) then you can snap-roll too. After all, a snap is just a horizontal spin, so I feel that you can snap any aircraft that you can spin and stay within the certified G forces that the airplane was tested to.
That's not to say that I recommend tearing up the sky in violation of the FAR's, just that it should be no problem WRT the airframe in most certified aircraft.
regards
~Marc
Last edited by Plummit on Mon Jan 08, 2007 5:51 am, edited 3 times in total.
John Renwick
Minneapolis, MN
Former owner, '55 C-170B, N4401B
'42 J-3 Cub, N62088
'50 Swift GC-1B, N2431B, Oshkosh 2009 Outstanding Swift Award, 2016 Best Continuously Maintained Swift
This is an interesting discussion, and brings back ancient memories when I was young and cocky (now I'm neither; well, certainly not young!)
In 1975 the Beech Aero Club I instructed at got a brand new, aerobatic version of the Sundowner. Flying solo, I taught myself aerobatics in that thing. I had the "experience" of extensive flying of R/C models, kind of like "Flight of the Phoenix" (He's crazy Lew; he builds toy airplanes - Jimmy Stewart.) Actually, it went well - but I would hardly recommend going this route.
This experience gave me the misguided confidence to roll non-aerobatic airplanes. The first was a American Avaition AA-1 Yankee, which
had a roll rate like a fighter, like 360 degrees in two seconds.
By then I was flying an Aero Commander 500 twin on charters in Key West, Fla. ferrying people like Jimmy Buffet to Miami (he wasn't a pilot yet.)
One day ferrying back to the Keys empty at 4500 feet, I decided to roll the Commander. Having seen Bob Hoover perform his magic in one a few weeks earlier no doubt had something to do with it. It rolled beautifully, in both directions.
After about the fifth one, I noticed the attitude indicator laying on its side -
it was TU after my little stunt. When I landed, I reported to the boss that the gyro horizon had died on the flight back from MIA. He narrowed his eyes to mere slits, and asked point-blank if I had been doing any aerobatics. In best "Right Stuff" form, I replied in the negative. Satisfied, he turned away - then mentioned casually that he had rolled it last year, screwing up the horizon indicator! 31 years later I can finally confess to the world...I feel better already!
The ultimate in unauthorized manuvers was Boeing test pilot "Tex" Johnson barrel-rolling the prototype 707 at the Seattle Hydroplane Races in 1955...twice! You can find it via Google, it's cool. Boeing's Pres called him on the carpet, and after he explained it was a 1G maneuver that involved no hazard to the priceless prototype, Mr. Allen said "You know it, now I know it...don't do it again" - and he didn't... Russ Farris
Years ago I watched Bob Hoover work his magic at Brackett field in a La Verne, CA airshow. After the show was over a military twin was departing and the hot-shot pilot threw in a roll for good measure.
Last I heard he was called on the carpet for busting FAR's , but the people on the ground appreciated it non the less.
Plummit wrote:...Correction, a G meter in an aircraft will register 0-G's of acceleration (1G) when straight and level. Pulling either positive or negative G's will indicate (at least on the accelerometers I've used) the maximum number of G's pulled. http://www.aircraftspruce.com/catalog/i ... meters.php
../ I maintain that if you have enough rudder to spin (which doesn't take much) then you can snap-roll too. After all, a snap is just a horizontal spin, so I feel that you can snap any aircraft that you can spin and stay within the certified G forces that the airplane was tested to.
That's not to say that I recommend tearing up the sky in violation of the FAR's, just that it should be no problem WRT the airframe in most certified aircraft.
regards
~Marc
Marc, I'd like to re-emphasize that spins in a 170 are performed at "slow deceleration". The spin-producing stall (below 55 mph) occurs well below manuevering speed.
A "snap" roll is an accelerated stall. In order to produce an accelerated stall in level flight, the angle of attack must be abruptly increased so as to produce the stall...at such a speed as to disallow altitude loss... and in order to provoke a spin/snap the rudder must be applied simultaneously. A snap roll is a level flight manuever with no loss of altitude. In order to accomplish this in a 170 one would have to have sufficient speed to enable the airplane to make the 360-degree roll with no altitude loss...with rudder being the causative factor producing the stall in one wing only. This will overstress a 170 beyond design load factors, and is why it is prohibited in a 170.
Will it absolutely cause airframe failure? Maybe not, but only due to the 150% factor designed into the airplane. I wouldn't want it done to my airplane, and I wouldn't want to fly in a 170 which had been subjected to such abuse.
The only G-meters I've ever seen, at rest will register 1-G.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
It's been a while since I've done a snap roll but IIRC. I didn't exceed 2 G's (the same as a 60 degree turn) in the Great Lakes I was flying. 2 G's are 2 G's are 2G's - and I maintain that if an A/C won't withstand 2G's then it shouldn't be flown - period.
Maneuvering speeds are designated as speeds where you can make full and abrupt control surface movenment with no damage. As for rotation, heck if you don't make any rudder input, engine torque will start you rotating (though not as fast) once you stall.
Am I recommending aerobatics in a 170? No, of course not. That's not to say that I don't feel a 170 can do basic postive G moves. And in all honesty, I wouldn't want to fly an A/C that I didn't feel was capable of 2 G maneuvers As always, YMMV.
regards
~Marc
gahorn wrote:
Plummit wrote:...Correction, a G meter in an aircraft will register 0-G's of acceleration (1G) when straight and level. Pulling either positive or negative G's will indicate (at least on the accelerometers I've used) the maximum number of G's pulled. http://www.aircraftspruce.com/catalog/i ... meters.php
../ I maintain that if you have enough rudder to spin (which doesn't take much) then you can snap-roll too. After all, a snap is just a horizontal spin, so I feel that you can snap any aircraft that you can spin and stay within the certified G forces that the airplane was tested to.
That's not to say that I recommend tearing up the sky in violation of the FAR's, just that it should be no problem WRT the airframe in most certified aircraft.
regards
~Marc
Marc, I'd like to re-emphasize that spins in a 170 are performed at "slow deceleration". The spin-producing stall (below 55 mph) occurs well below manuevering speed.
A "snap" roll is an accelerated stall. In order to produce an accelerated stall in level flight, the angle of attack must be abruptly increased so as to produce the stall...at such a speed as to disallow altitude loss... and in order to provoke a spin/snap the rudder must be applied simultaneously. A snap roll is a level flight manuever with no loss of altitude. In order to accomplish this in a 170 one would have to have sufficient speed to enable the airplane to make the 360-degree roll with no altitude loss...with rudder being the causative factor producing the stall in one wing only. This will overstress a 170 beyond design load factors, and is why it is prohibited in a 170.
Will it absolutely cause airframe failure? Maybe not, but only due to the 150% factor designed into the airplane. I wouldn't want it done to my airplane, and I wouldn't want to fly in a 170 which had been subjected to such abuse.
The only G-meters I've ever seen, at rest will register 1-G.
I know we're only talking theoreticals here, Marc, but....
Consideration of positive G-forces alone is not a comprehensive evaluation of stresses upon the airframe. There are twisting forces, and additional stresses upon control-surface hinges and tailplane structure that a simple measurement of positive G-forces does not take into account.
If the manufacturer and the certification authority do not approve the manuever for the airplane, then the opinion of a pilot/owner doesn't carry sufficient weight to warrant it either. I'd simply hate it if someone reading these comments based a decision to attempt a snap roll in this airplane upon comments which are in direct opposition to the designers/builders of the airplane. IMHO.
The vast majority of aircraft in the world are not approved for such manuevers, but I'm happy to fly in most of them....as long as the pilot doesn't attempt unapproved manuevers.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
dacker wrote:Gee George, I guess you also call it ACROBATICS! ...
I couldn't help myself. The following is quoted from our airplane's Type Certificate: "No acrobatic maneuvers approved except those listed in the Airplane Flight Manual..." I guess aerobatics are OK.
(I suppose that night flight I made in the Aeronca Chief was OK since it was approved for acrobatics.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
gahorn wrote:I know we're only talking theoreticals here, Marc, but....
I'd simply hate it if someone reading these comments based a decision to attempt a snap roll in this airplane upon comments which are in direct opposition to the designers/builders of the airplane. IMHO.
The vast majority of aircraft in the world are not approved for such manuevers, but I'm happy to fly in most of them....as long as the pilot doesn't attempt unapproved manuevers.
My gawd Geroge, re-read my comments! No where am I proposing using a 170 for aerobatics. The point I am trying to make is that a snap roll (or spin for that matter) will not stress a 170 beyond what it is designed for. Of course we say don't do it, but we also recommend flying with strict adherence to the weight and balance. How many times do you think that a 4-seat 170 has been flown beyond its mximum gross weight rating? Would you fly in an aircraft that you know has been over-loaded in the past?
To me flying an aircraft that has been overloaded is more hazarous than flying one that has never been stressed beyond its certified G limits. If you fly in turbulent conditions (such as mountain wave) and you do so responsibly (which means you follow the airspeed guidelines) you should have nothing to worry about.
Again, I'm not recommending using a 170 for aerobatic flight, and I hardly think that us musing about the relative effects and hazards will be translated by anyone as a free pass to wring-out any aircraft that is not approved for such flight.
That, as they say, is my opinion and I'm sticking to it!
What about flying with an acrobat?
I guess I have to give the FAA a break and retract my statement about them using the term acrobatics... I know that I have seen them reference it somewhere but I don't know where. In the FARs at least they correctly use the term aerobatics.
David
Thanks, Marc. Yes I saw your earlier disclaimer, ... I simply disagree with you about whether or not it'll overstress the airplane. While attempting such a manuever below manuevering speed isn't supposed to hurt a brand new, no-defect airplane... It will also not result in a snap roll in a 170. It will result in a spin or a descending spiral that rapidly approaches airspeed limits for the airframe, if attempted below manuevering speed.
And, at higher speeds it'll result in an overstressed airplane. IMHO
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
The BO 105 is an amazing helicopter, old, but amazing. It has a rigid rotor system which allows it to make that sort of maneuver (As do most modern combat helicopters). For the uninitiated, many helicopters have teetering rotor systems that would snap off if subjected to negative G push overs like what was demonstrated. Not a pretty sight.
I bet Bruce has a little BO105 time!
David
Bill that is the MBB BO 105 which the German military flies. This is probably many years old as the 105 is going by the way side.
The BK117 I fly is the 105s bigger brother and is supposed to be every bit as aerobatic. I can only tell you it has one hell of a roll rate, rolling 90.. I mean 60 degrees in a blink.
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
David no 105 time yet but our company has some. To be more correct the 105 and the 117 have a semi rigid rotor. (it's pretty darn rigid).
The EC135 which is the modern day BO105 has a true bearing-less rigid rotor head. I thought the BK117 had a fast roll rate till I got checked out in a EC135. You don't flinch on the cyclic, you'll be on you side. WOW.
CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
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