Old Dog Flying wrote:The airflow in the flat spin mode is perpendicular to the bottom of the horizontal tail blanking off the rudder which of course makes stopping the autorotation impossible.Barney
That's a very common-sense explanation, Barney: thank you.
Obviously this isn't an issue in an inverted flat spin, per CS's video just above. It does raise the question, though: if you can't stop the autorotation, how on earth does one recover from a flat spin (bearing in mind that . Yeager had a problem with that type of recovery on at least one occasion - cue the very memorable 104 flat spin scene from The Right Stuff)?
I`m no expert in flat spins in anything but with the Grumman AA1x series, one thought is to slide the canopy back about one foot and hold on. I`ve opened the canopy while my wife was flying and the nose pitched down very rapidly..from level flight...but I have no intention of trying it in a spin!
The canopy can be opened in flight about 6 inches, legally, below 130 mph. Noisy as hell though.
This just might force the nose down causing a change in the relative airflow which just might make the rudder effective enough to recover from the spin.
In piston aircraft, we flatten the spin (raise the nose) by
using gyroscopic precession of the propeller. Hence with
a Lycoming or Continental, which rotates clockwise when
viewed from behind, we can only flatten left-yaw upright
spins, or right-yaw inverted spins.
The inverted flat spin is a pussycat, because I can stop it
in 1/4 of a rotation. Thusly, it can be safely entered and
exited at very low altitude. The reason for this is that the
large portion of the top of the rudder is in clean air, and
has lots of authority to stop the yawing of the spin.
However, the upright flat spin must be treated with respect,
and entered with plenty of altitude. As Barney points out,
there is precious little of the rudder underneath the elevator -
it is the only portion in clean air. The portion of the rudder
above the elevator is blanketed and is not very effective.
Because of this, it can take 2 full turns of the upright flat
spin before it exits - with full anti-spin rudder! The problem
is that people are pumped and lose the faith - when they
don't get an instant stoppage of the spin they panic and
try something else. Bad news.
Anyways that's probably too much technical garbage, but
I love inverted flat spins. So do most other airshow pilots.
Note that I would not spin a larger aircraft, because of the
problem of polar moment of inertia.
Technical detail: we can have two identically-appearing aircraft
with the exact same weight and balance, and one is easy to
recover from a spin, and the other cannot be recovered.
How can that be, you ask? You will tell me, "My instructor told
me that if my C of G was in the right place, I was safe". Well,
your instructor hasn't a clue about PMI - integral radius squared
dm probably wasn't mentioned at his puppy mill.
Take a carton of eggs with only 4 eggs in it, in the center slots,
and put your hand on the middle of it on a shiny counter, and
rotate it back and forth as viewed from above. See how easy
it is, to start and stop it?
Now take the 4 eggs and put two at each end, and repeat the
same test. See how much harder it is, to start and stop the
rotation with your wrist? That's because although the W&B is
exactly the same, your PMI is much greater!
An aircraft with all of it's mass concentrated at the center is
going to be easy to start and stop spinning. If it has mass
at the ends, it's going to really want to rotate.
Nobody cares about this kind of thing but me, but ...
There was once a little lady called Kathy Jaffe that flew a
Pitts. She didn't weigh very much, so she put some scuba
weights - not much - in the back of her Pitts. She went up,
did a spin, and rotated right into the ground where she died.
None of you have ever heard of Kathy Jaffe, but she's still
dead.
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Last edited by Colonel Sanders on Tue Apr 24, 2012 5:53 pm, edited 1 time in total.
Old Dog and CS, that makes sense - thanks. Here's hoping I never have to try to keep the faith!
Found Yeager's flat spin segment (NF104) in The Right Stuff. I had forgotten what a beautiful airplane the 104 was - and what a terrific movie it is!
Please remember how Art Scholl died - in a flat spin
in a Pitts, filming a sequence for Top Gun.
Now children, how would a camera strapped to the
extremity of an aircraft affect it's Polar Moment of
Intertia?
Art is still dead, too.
P.S. The F-104 was an amazing aircraft, when you
consider the dark ages (early 1950's) that it emerged
from. It didn't do very much very well except go very
fast and very high. Like other T-tail aircraft, it suffering
from a pitch-up problem if it was stalled. I would not
recommend stalling or spinning an F-104 if you want
to get a whole lot older. Fortunately the F-104 was
equipped with an equivalent angle of attack indicator
and as long as you kept it less than 17 degrees, it
flew very well - even if you flew it very slowly. It
did a marvellous hammerhead, btw.
The RCAF certainly went through its share of 104s back in the day. One of the funniest (in a twisted kind of way) comments to appear on this forum was a contribution on this topic by iflyforpie last April: "Usually the best way to acquire a Starfighter was to buy a small farm in Germany and wait. Maybe fishing nets would work too..."
iflyforpie is amusing in a left-wing manner, but his grasp of the facts is a little loose in this case, as is typical of left-wing people. The RCAF was not exactly the sole operator of -104's in Europe.
It was actually the Germans who had a horrible problem with the F-104G over in Europe, mostly because their pilots had not gone through the Sabre years in the 1950's that the RCAF did. Even left-wing people can probably recall WWII, and that for a time afterwards, the Germans were not allowed to have a military.
The Germans lacked seasoned wing commanders and group captains to tell their pilots what was safe, and wasn't safe, with horrible consequences.
Colonel Sanders wrote:
There was once a little lady called Kathy Jaffe that flew a
Pitts. She didn't weigh very much, so she put some scuba
weights - not much - in the back of her Pitts.
WHY.. CofG might have something to do with it. I was instructing in a Chipmunk (rear seat) and doing a Cuban 8..on the down line while rolling to the upright the damned thing did a 1 and a half snap to the upright then did it again during the last half of the Eight.
I weighed 210 lbs at the time and when I did a weight and balance later, we were at the rearmost of the envelope.
If I remember correctly she was observed by another pilot who stated he felt she had crossed over to inverted.
There was a lot of analysis that went on and some facts came to light which may or may not have been relevant. One was that she added ballast to shift her C of G aft a bit. A small person in a single seat Pitts does have a forward C of G and a Pitts definitely snaps/spins with less effort with a rear C of G but as long as the ballast is added correctly its not an issue. In this case she strapped the weights to the rear of her seat .. which should not have changed her polar moment of inertia much, but is dangerous if it comes loose, which it did not apparently.
There were other discussions about how she was aiming to get a clean spin entry and clean exit. In competition we are judged on 'crispness' of what we do and that usually means you have to be very agressive with the stick. Its possible that she was over agressive in the recovery and in a Pitts/Extra or other aerobatic plane .. if you push the stick forward crisply and slam in the opposite rudder at the wrong time the plane beautifully transitions into an inverted spin which from the outside is of course the same direction but for which your recovery inputs are now inverted spin inputs. The problem is made worse in a bubble canopy plane .. which most aerobatic planes are .. because your tendency is to look up back at the ground.. this gives you the illusion you are rotating in the oposite direction than you get when looking over the nose.
For this reason spin recovery in these kinds of planes is not done aggressively, you usually just give it the required input, especially elevator. No harm with full rudder but full agressive elevator , especially if held is not wise. Upset recovery training also teaches you were to look .. over the nose.. and they also teach go with the flow. Which means to push the rudder to the side you see the flow going. This is because some of these planes rotate so fast (400 degrees a second or so) you don't actually see anything except a blurr and determining rotation direction is confusing. So .. "go with the flow".
The feeling in her case was the she had crossed over from upright to inverted likely by being too agressive. She may have hammered the throttle early too .. something we try to do to minimize energy loss. The lead weights possibly contributing as they would have changed the spin characteristics a bit, but should not have made it unrecoverable as they were attached to the seat back. Had she attached less weight to the tail .. that could have made a big difference to the polar moment of inertia which is probably what CS was alluding to .. but I believe in this case it was not a factor.
Bottom line .. training. She did not have any inverted spin training and these aircraft its pretty important. Her desire to get a crisp entry and exit may have resulted in agressive elevator and power application which if not timed perfectly gets you somewhere mightly confusing the first time you see it.
I did a whack load of spin training in Pitts/Extras etc. before getting mine and even then had a bit of fun the first time I did an inverted spin in it. Every time I recovered she popped immediately into an opposite direction inverted spin. As CS points out the rudder is super effective inverted and recovery only required a quick jab, while upright a more prounounced and longer push is required. Took a couple of rotation direction changes for me to lighten up on the pedals.
Sorry to bust in on this post, however the site won't let me post on the marketplace? 172pilot do you still have the Garmin aera for sale? e-mail me at ji@muleys.ca
Again all, sorry.
Colonel Sanders wrote:iflyforpie is amusing in a left-wing manner, but his grasp of the facts is a little loose in this case, as is typical of left-wing people. The RCAF was not exactly the sole operator of -104's in Europe.
It was actually the Germans who had a horrible problem with the F-104G over in Europe, mostly because their pilots had not gone through the Sabre years in the 1950's that the RCAF did. Even left-wing people can probably recall WWII, and that for a time afterwards, the Germans were not allowed to have a military.
The Germans lacked seasoned wing commanders and group captains to tell their pilots what was safe, and wasn't safe, with horrible consequences.
To be fair, the RCAF comment was mine, not iflyfor pie's - his comment was limited to the phrase in between the quotation marks.
And I was definitely aware that the RCAF was not the sole operator of 104s, and that the Luftwaffe did have a terrible problem with that aircraft. I had understood it was because, like the RCAF, they used an aircraft designed for high-altitude intercept in a ground support role - any truth to that? Your comment above about the lack of a seasoned training staff is one I hadn't seen before, but it makes sense.
they used an aircraft designed for high-altitude intercept in a ground support role - any truth to that?
The -104 was used in many ways it wasn't initially intended.
My father, who was at CEPE at Cold Lake in the early 60's, was the first to demonstrate a low-altitude bomb run in IMC, which is a nice aerobatic demonstration. All sorts of personages said it couldn't be done, but that's the role it took on in Europe for the RCAF - low altitude ingress nuclear bomber.
And since it had the marvellous M61 Gatling gun - used on many, many other types since then - it could simply pulverize anything on the ground with it.
However the high speed of the -104 (300 knots is slow) made it a very poor choice for CAS, IMHO.
The M61 and its derivatives have been the principal cannon armament of United States military fixed-wing aircraft for fifty years.
The first aircraft to carry the M61A1 was the C model of the F-104, starting in 1959.
A lighter version of the Vulcan developed for use on the F-22 Raptor, the M61A2, is mechanically the same as the M61A1, but with thinner barrels to reduce overall weight to 202 pounds (92 kg). The rotor and housing have also been modified to remove any piece of metal not absolutely needed for operation and replaces some metal components with lighter weight materials. The F/A-18E/F also uses this version.
The Vulcan's rate of fire is typically 6,000 rounds per minute, although some versions (such as that of the AMX and the F-106 Delta Dart) are limited to a lower rate, and others have a selectable rate of fire of either 4,000 or 6,000 rounds per minute. The M61A2's lighter barrels allow a somewhat higher rate of fire up to 6,600 rounds per minute
I've never had a problem with upright vs inverted - frankly I don't really care, because a spin is all about yaw - but this reminds me, a few days ago I met a fellow who got some aerobatic instruction from Gerry in the 2-seat Pitts, many years ago, and insisted upon telling me this story.
At the time, he was a young instructor that wanted to fly aerobatics in his Citabria back east, but there was no one to teach him to fly it, so he went to Gerry and asked him to teach him how to do some gentle rolls and loops.
So, no ground briefing, which slightly concerned the young instructor. They pull to the vertical, and Gerry says, "this is an inverted spin", and he applies full forward stick and then full left rudder, and off they went.
Colonel Sanders wrote:iflyforpie is amusing in a left-wing manner, but his grasp of the facts is a little loose in this case, as is typical of left-wing people. The RCAF was not exactly the sole operator of -104's in Europe.
It was actually the Germans who had a horrible problem with the F-104G over in Europe, mostly because their pilots had not gone through the Sabre years in the 1950's that the RCAF did. Even left-wing people can probably recall WWII, and that for a time afterwards, the Germans were not allowed to have a military.
The Germans lacked seasoned wing commanders and group captains to tell their pilots what was safe, and wasn't safe, with horrible consequences.
While you're a really smart guy physics wise, occassionally your historical facts are out to lunch. A photo is worth a thousand words.
Incidentally that's the one marked in Hartmann's personal markings, who did work for the Luftwaffe at the time, though was fired over his critisism on how the Germans were using and training on the 104. They were equipped with Sabres from 1957 to 1964 before transitioning to 104s.
You see what happens when you bring in the political binary CS? Logic breaks down and your credibility goes out the window in spite of all you have to offer on this forum.
My tongue-in-cheek comment was based on fact and on the operation of the 104 in Europe by the Luftwaffe, in which they lost 110 pilots.
It's pretty unfair to say that it was lack of experience on the part of the Germans as well. In addition to Erich Hartman and indeed operating F-86s, they also had pilots like Johannes Steinhoff, who was one of the first jet pilots in the world flying the 262.
I don't know a lot about the 104 but I did gain some knowledge of the operations in the CAF since much of my CPL was under the tutorage of a former 104 driver.
Read Gunther Rall's biography a couple months back -- the Luftwaffe general in charge of integrating the 104 -- and he seemed to blame the Germans' high accident rate on a differing aviation mentality the Germans still had as a hold over from the war. They had quite a few experienced old aces (including himself as the third highest scoring ace of all time) -- so I'm pretty sure experience wasn't an issue.
He mentions the old cadre were not yet accustomed to the widespread use of checklists and the strict safety and training standards that were already common place with American pilots, and combined with the 104s unforgiving nature he cites that as the reason they got bit in the ass so badly. Maybe a case of too much experience from the old trainers, who can't pass on their experience effectively without the proper training tools and safety culture?
He mentions the old cadre were not yet accustomed to the widespread use of checklists and the strict safety and training standards that were already common place with American pilots, and combined with the 104s unforgiving nature he cites that as the reason they got bit in the ass so badly. Maybe a case of too much experience from the old trainers, who can't pass on their experience effectively without the proper training tools and safety culture?
Partly, but not entirely. The issue has interesting parallels with some of the busier arguements today. At the time there was a big push from the political side of things to get more airplanes in service and obviously shortcuts were taken. Often cited by Rall and others was a lack of training for flying low level, as well as a lack of instrument training as compared to the Lockheed training, and other 104 users at the time. Only after political pressure swung the other way - where not crashing airplanes finally became more important to the populace, than say the security they felt was needed to keep the Reds at bay (amongst other things), that they started listening to the old guys again and those still in the structure like Rall were able to make the change.
edit:
He mentions the old cadre were not yet accustomed to the widespread use of checklists and the strict safety and training standards that were already common place with American pilots,
I'd find this assessment a little hard to believe personally. Follow rules is what Germans do. Have you met these people? Someone just obviously didn't give them enough rules to fly the 104. Nothing more chaotic than a bunch of Germans without a rulebook.
itterble wrote:Sorry to bust in on this post, however the site won't let me post on the marketplace? 172pilot do you still have the Garmin aera for sale? e-mail me at ji@muleys.ca
Again all, sorry.
You need more posts. The board is set up that way to reduce spammers. I'll PM him for you.
I'd find this assessment a little hard to believe personally. Follow rules is what Germans do. Have you met these people? Someone just obviously didn't give them enough rules to fly the 104. Nothing more chaotic than a bunch of Germans without a rulebook.
Don't take my word for it -- read his autobiography if you're interested. He explicitly mentions the differences in aviation safety mentality between the luftwaffe of WW2 vs. the Americans, post-ww2. The heavy reliance on checklists and SOPs was a bit foreign to the grizzled old eastern front vets of the german luftwaffe, but in his opinion, ended up being required for the safe transition to the jet age.
... but I am of course just citing this from memory. I could be muddling what he was trying to say a bit.
