CAtegories and Manoeuvres

[Ric00]

Hi!
I was wondering what kind of manoeuvres are certified on the PA38 Tomahawk.
Also why on the Utility category the loop, spin and barrel roll are permitted but the whip stall is not?

Regards,

R.

[englishal]

Probably because the whip stall will overstress something in the aeroplane.

Main Entry: whip stall
: a stall during a vertical climb in which the nose of the airplane whips violently forward and then downward

[Captain Smithy]

Loop and barrel roll approved on a Tomahawk? Since when? :confused:

Spins are prohibited in all cases, it's placarded on ours.

Smithy

[Mark1234]

Don't know about loops and rolls, but I'm pretty sure the Tomahawk *is* allowed to be spun - it's their spinning characteristics that earned the 'traumahawk' moniker.

Your placards may be due to operator regs, or possibly AD's that haven't been applied, though I'd expect those would be up to date.

Ric00: Short answer is read the POH!

[mad_jock]

PA38 is allowed to spin in the UK under certain conditions.

It must have a 5 point harness fitted and the C of G must be between certain limts and about 6 mods have to be have done to the tail.

A loop and barrel roll is not permitted in the UK although I am sure someone has done them.

The POH is your bible

[hatzflyer]

I'd like to meet the person that looped and rolled a Tomahawk...( or at least put some flowers on their grave.).:hmm:

[mad_jock]

You won't die doing either of those manoeuvres in a PA38.

The loop will shag the engine because its not built for it but the aircraft won't drop out of the sky or the tail fall off. Students recovering from spiral dives when the speed gets up, pull way more G than a loop. Its a function of the oil system on the engine amongst other things

Barrel roll in the right hands (not mine I may add) will not do anything at all to the aircraft. Allegedly Concorde did one may years ago.

Its a matter of the certification. As I said before I am sure these manoeuvres have been done before but I certainly wouldn't recommend it and I will never be in a PA38 when it does them.

[Mark1234]

You won't die doing either of those manoeuvres in a PA38.
Unless the owner / school / CAA catch you :)

[mad_jock]

Good point well presented.

Although along the barrel roll side of things it is usually do as I say not as I do. The Concorde case being the point in proof.

The old 707 did a barrel roll as well much to Boeings upset.

[BackPacker]

The loop will shag the engine because its not built for it [...] Its a function of the oil system on the engine amongst other things

Could you expand on this a little? Is the oil pump not capable of pumping the oil 20 cm or so into 4G or am I reading this incorrectly?

You won't die doing either of those manoeuvres properly in a PA38.

Fixed that for you.

The problem of course is when you fail to do them properly. In both manoeuvres you might end up nose-down, approaching Vne and needing way too much up elevator to recover from the dive, overstressing the airframe, engine mount, you name it. If you roll at the same time those forces are increased at the wing roots, leading to bent wings or worse.

Aerobatic aircraft have sufficient strength in reserve to survive most wrongly executed manoeuvres, and that's why you should be practicing aeros in an aircraft certified for them. Rumour has it that the Concorde, the 707 and a few more airliners have been looped and/or barrel-rolled. But this was not done by novice aerobatics pilots.

[Captain Smithy]

The thing with the old 707 story was that Tex Johnston managed to keep a constant 1g throughout the manoeuvre. He knew what he was doing, which is why he was Boeing's chief test pilot.

In theory it's entirely possible with any aeroplane, as long as you keep at a constant 1g. Of course, it's not exactly legal with most aeroplanes, and for good reason.

There was an accident a while back in America when a pilot with no aerobatic experience attempted to barrel roll a Beech Baron, a la Tex in the 707 prototype. The wings fell off and what was left of the Baron sans aerofoils fell to Earth rather quickly, along with its unfortunate pilot. Oops :uhoh:

Smithy

[mad_jock]

Could you expand on this a little? Is the oil pump not capable of pumping the oil 20 cm or so into 4G or am I reading this incorrectly?

I believe and I am quite willing to be wrong on this.

Most none aero engines have wet sumps and the oil is pumped directly from there. Aerobatic engines have scavenger pumps in the sump which then take it to a tank which means when you play silly sods a supply of oil is maintained to the bits that need it. And even if that's bollocks its as good a reason as any for me not to do aero's in a PA38.

And as for the rest of your post you are spot on in my view.

[Mark1234]

Ok, I did wonder about that, but wasn't going to open the door.. as backpacker has: Hypothetically it should be perfectly possible to complete a loop with mild and entirely positive G, within the certified G limits of the aeroplane. It won't be round, but...

Barrel roll is probably one of the nastier ones if done as a proper barrel roll (rolling G), let's not start the 'is a one G manouver' misconception. What a lot of people call a barrel roll is really an aileron roll and not half as bad..

As has been said, there's no reason the wings would fall off, but there's very little margin for error, and very good reason to do so.

The aforementioned whip stall sounds a lot like a tailslide, or at least something that could very easily turn into a tailslide - in which case the biggest likelyhood of damage through mishandling is to the tailfeathers. As anecdotally they seem to flap around a bit on the '38 (never flown one), that would seem a good reason to avoid.

Quite simply there are plenty of perfectly good aerobatic aircraft out there designed to take the stresses, and also to leave you a reasonable chance of getting away with minor stuffups. Why risk it?

[Lightning Mate]

If we disregard the legalities for a moment, a barrel roll may be performed with very little g.

The usual mistake made by novices is not getting the nose high enough at the start. This leads to a buried nose scenario in the second half, and that's when it goes wrong.

Trust me here. I am a retired QFI (RAF) and aerobatics pilot with three trophies to my name, one of them very prestigious.

[BackPacker]

Aerobatic engines have scavenger pumps in the sump which then take it to a tank which means when you play silly sods a supply of oil is maintained to the bits that need it.

Okay, I get your point. I don't think you're entirely correct, but I'm not sure. But I think it all comes down to "what's an aerobatic aircraft".

I personally fly the Robin R2160 (and, coincidentally, so does Mark1234). As far as I know the engine is completely identical to what's mounted on, say, a DR400-160 with the one exception and that is that there's a cup or something to prevent the oil from leaking out through the breather pipe when inverted. (Still, anything over 5 quarts is chucked out anyway.) Even the dipstick is in the same place, so I assume this engine has a wet sump too.

When pulling positive Gs (the airframe is certified to 6 G) there are no limitations whatsoever. As far as the manufacturer is concerned you can pull that all day. So I assume the oil pump is fully capable of supplying the engine with sufficient oil even in relatively high-g manoeuvers.

The catch with this engine is of course the negative Gs. The wet sump means that the oil pump will run dry, no longer supplying oil to the engine. Because of this all inverted manoeuvres are limited to 20 seconds or less - we use 10 seconds for additional safety margin.

So what triggered my post was your suggestion that during positive G manoeuvres (loop, barrel roll) in a PA-38 you would shag the engine because the oil pump would not cope. I think this is incorrect. But you would definitely shag the engine in a relatively short time with negative G manoeuvers.

[englishal]

Our Rallye is cleared for loops, rolls, stall turns, spins etc., and has a normal O320 engine.....

[mad_jock]

I can live with your description why it shouldn't shag the engine.

But I still ain't going to loop a PA38 :p or even sit in one while someone else does.

[the dean]

Ric00....

i'd like to see where you got that info...

i instructed in a PA38 for 15 years....we spun it but thats it....:=...(four point harness permitted in our jurisdiction.....)

primary rule in this or stalls..( but used to invite the student to do it)....do'nt look at the tail......!!!!!!!:eek:

[Lightning Mate]

....????!!!!...cuk :ugh:

[1800ed]

Just think about all the people who will be questioning your intentions in club houses all over the country and on here when the AAIB report is published if you try something silly and bugger it up.

[Mark1234]

Would the 1G mob please go away and think - ANY time you accelerate the aircraft away from a straight path, you are no longer at 1G.

This is what I'd call an aileron roll (Tex)
YouTube - Boeing 707 roll by Test Pilot Tex Johnson (http://www.youtube.com/watch?v=Ra_khhzuFlE)
It's a low G manouver. >1 on the pullup, usually <1 but >0 on the inverted section. Why he calls it a barrel roll i'll never know. Simplification for the audience?

This is a BARREL roll. Rather different:
YouTube - T6 Training Video. Barrel Rolls (http://www.youtube.com/watch?v=3gBxCShr1_g)
The defining characteristics as I understand are a large heading displacement and the helical path of the aircraft. Consider it to be rolling the wheels around the inside of a tube (or barrel), hence the name.
In fact, it's almost a loop and a roll combined. I'm usually pulling at least 2.5 through the last part, frequently more, though I'll freely admit that they rank as the single figure I fluff most often (and they're not in the aresti catalog anyway).

Then you have an axial roll where you do NOT pull up; the aircraft travels along a straight, level path whilst rolling; you use top rudder (knife edge), forward stick (-1G), then opposite knife on the way around.

Best though, forget all that and go do flicks/snaps. But definately NOT in the traumahawk :E

@mad_jock, BackPacker - both right; I'd not be sat in it while somebody looped it, but wet sumps are not uncommon in aerobatic (training) a/c. The robin is wet sumped. The better aerobatic a/c do indeed have inverted oil based on a scavenge system, they also tend to arrange for the engine to continue making noise upside down too! Oh, and the proper name for the 'cup' is a catch tank I think :)

[englishal]

Yes it is a physical impossibility to barrel roll and not exceed 1g. Might be able to do it with 2g or less though.

Anytime you have vertical accelleration 1g will be exceeded or reduced.

[Runaway Gun]

A Tomahawk simply isn't safe to do those manouevres in (loops, barrel rolls, tailslides, stall turns, or high-G pullups when you stuff them up).

If you want to do it without risking your life (or the life of the next poor pilot who hops in it), then go and do a proper aerobatic course, in a certified aerobatic aircraft.

[englishal]

The tomahawk is perfectly safe to do those manouevres in.....it is the pilot who may not be safe.

[Captain Smithy]

Let me get this straight. There are people here advocating that it is acceptable to perform aerobatic manoeuvres in a non-aerobatic aeroplane.

A bemused Smithy

[englishal]

No....But pretty much any aeroplane is capable of aerobatics if done correctly.

There is an excellent video of Bob Hoover demonstrating aeros in a Rockwell Commander 114, for example. There is also a vid of the Eclipse Jet doing aerobatics at a demonstration, not to mention the famous 707 barrel roll.

Not advocating it, just pointing out that it is indeed possible.

[DB6]

Most light aircraft in the utility category are certified to +4.4/-2 g (ish). It is perfectly possible to fly aerobatics well within these limits, and it doesn't matter whether you have an engine with inverted sytems or not unless you are going to do significant inverted flying e.g. Cessna Aerobats don't. Where it might all go horribly wrong is if you bugger it up, have to pull 6 g or go way past Vne to recover from a botched manoeuvre and the wings decide otherwise - or during the next few flights when someone else is maybe practicing steep turns, since the effects of g on an airframe are cumulative - so it's not the best idea to aerobat non-aerobatic aircraft but it's not impossible or even dangerous if properly done. It's just that there are no margins for error so is it wise? Ahem - you decide. Incidentally the other thing that will get hammered is the engine as the rpm goes way past the red line......

[foxmoth]

Incidentally the other thing that will get hammered is the engine as the rpm goes way past the red line......

Again only if you have not been properly trained and just as likely in an Aerobatic machine with a fixed pitch prop as a non aero machine. I LOVE aeros, but when I first turned up at the flying club in Bournemouth most instructors were away at the funeral of one of the members who had been aeroing a (non aerobat) C150 so you will NOT find ME turning a non aero machine upside down:eek:

[Mark1234]

Absolutely NOT advocating aeros in a non certified machine. All sorts of things are possible, if you're very good, and have thought it through carefully. However, people like Bob hoover know exactly what they've got to play with, and have done it all before in aircraft with bigger margins. The have a go heroes make the accident reports.

G limits are even more complex than you may think - the +4.4/-2 DB6 quotes, and even the +6/-4 of the a typical aeros trainer are pitch plane limits. They assume all you do is heave the stick back (or forward). Once you start rolling and pulling G, it's more complex; there are torsional factors, and one side is being accelerated more than the other. Some (few) a/c provide numbers for rolling G, limits. Mostly common practice seems to be to knock 1/3 off - so if it's +6, you don't pull >4 while rolling etc. Personally I try to keep it to less than that..

I would suggest very strongly that aerobatics are something you learn with a good and trustworthy instructor. They are not in themselves particularly difficult, however when things go wrong, they can do so very quickly - A significant part of training is how to escape from botched manouvers. Nearly lost a good friend of mine recently - he flies aeros every weekend, but despite all that, had 'brain fart' when all didn't go as it should - he nearly peeled the wings off, and scared himself half to death.

This sort of forum talk is all well and good, but it's not flight simulator out there, there is no reset button. Anyway, let's face it, most aerobatic aircraft are straight out FAR more fun to fly than their non-aerobatic bretheren.. so why not get into something fun?

[BackPacker]

G limits are even more complex than you may think - the +4.4/-2 DB6 quotes, and even the +6/-4 of the a typical aeros trainer are pitch plane limits. They assume all you do is heave the stick back (or forward). Once you start rolling and pulling G, it's more complex; there are torsional factors, and one side is being accelerated more than the other. Some (few) a/c provide numbers for rolling G, limits. Mostly common practice seems to be to knock 1/3 off - so if it's +6, you don't pull >4 while rolling etc. Personally I try to keep it to less than that..

To make matters worse, flying below Va also doesn't offer any protection against rolling and pitching simultaneously. And if you want to use full deflection on the rudder, better be well below Va - aerobatic aircraft typically have separate numbers for full rudder deflection limits. In the R2160, Va is a whopping 127 knots, while full rudder deflection (leading to a snap roll) has to be done below 92 knots.

Aerobatics is complex stuff and not a Learn-it-Yourself activity. Let alone in a non-aerobatics aircraft.

[foxmoth]

A significant part of training is how to escape from botched manouvers.

Exactly so - If I check someone for aeros I am not concerned if they cannot do a perfect Loop or Barrel Roll, what I do want to see is that they are competent on Spin and Unnusual Attitude recoveries:ok:

[hatzflyer]

At last we are getting some common sense. People ( my self included when I was young and wet behind the ears) often quote the fact that you can barrel roll anything.
Not many people know what a true barrel roll is, even fewer know that statistically botched barrel rolls kill more people that any other manouvre.

707's have been rolled, Bob Hoover can probably roll anything, but people like him are not normal pilots and they are definately not students.
People like Steve Davis can clear a snooker table in one go and make it look easy, just as Bob makes aeros look easy,but the differance is if Steve fails he may have a red face but thats all.....failure in flying costs lives.

I botched a roll once and blacked out in the recovery, everyone on the ground said it looked spectacular. It scared me to death and I was in an aircraft designed for 9g.
I wish I could do a mind transfer and share that experience on this thread... trust me you would not wish to go there !

[englishal]

I've botched a loop before, and ended up falling from the top......with style ;) Also I found the barrel roll exceedingly tricky to do.

Regarding G limits, in a rolling manoeuvre like a BR, the g limits are effectively halved which is why it would be nice to have at least +6/-3G.