Ask The Pilot

[jb747]

Extract from the A4G flight manual.

Flight tests and spin tunnel model tests indicate spin
recovery is possible in all configurations. The air-
craft proved reluctant to enter a fully developed spin
unless pro spin control is applied and maintained.
Erect spins resulted from noseup elevator control
and inverted spins from nosedown elevator control.
The aircraft oscillates about all axes in a spin, with
erect spins being the most oscillatory. A 360-degree
roll occurs during the first one to three turns of an
erect spin. Bank oscillations decrease to about 60
degrees after the third turn of an erect spin. The
aircraft pitches from near level to a 70-degree nose-
down attitude during each turn. There is a hesitation
in spin rotation at the completion of each turn in the
spin. Spin rotation varies from 5 to 10 seconds per
turn with an altitude loss of 3000 to 5000 feet per
turn. Faster spin rotation rates result in lower
altitude loss per turn. Slower spin rotation rates
result in greater altitude loss per turn. Rate of
descent will vary from 30,000 to 36,000 feet per
minute, depending on the steepness and rotation
rate of the particular spin. Load factors of 1. 0 to
3.5g have been experienced during the spin.
Erect spins entered from an accelerated stall have
the same characteristics as 1. Og-spin entries except
that snap-roll type maneuvers occur during the first
two or three turns. Erect spin characteristics with
external stores are the same as the clean aircraft
except that the oscillations occur at a lower
frequency.
Relatively flat, erect spins have developed after
several steep turns such as described above. There
is no hesitation in spin rotation and the rate is very
fast: 3 seconds per turn with an altitude loss of 1500
to 2000 feet per turn. Rate of descent will vary from
30,000 to 40,000 feet per minute. Aircraft pitch
oscillations vary from 25 to 50 degrees nosedown and
oscillations vary between 20 degrees left and right wing down.


Inverted spin characteristics with or without external
stores are the same. The aircraft abruptly whips
into an inverted spin when the necessary conditions
are established: forward elevator control developing
a negative load factor while the aircraft is simulta-
neously yawing and rolling to an inverted attitude. A
fully developed inverted spin occurs within one turn.
The spin is relatively flat at a fast rate: 3 seconds
per turn with an altitude loss of 800 to 1500 feet per
turn. Rate of descent will vary from 16,000 to 30,000
feet per minute. Aircraft, pitch oscillations vary
between 20 to 50 degrees nosedown while bank oscil-
lations vary between 30 degrees left and right wing
down about an inverted attitude. Negative load factors
of 0.5 to 1. Og have been experienced during an
inverted spin. '

WARNING
If an inadvertent confirmed spin occurs
below 10,000 feet AGL, eject. Recovery
from a fully developed spin below 10,000
feet is considered doubtful since 5000 to
7000 feet are required to complete recovery
with proper application of the controls.
Recovery from an inadvertent incipient spin
may be accomplished with altitude losses
varying from 0 to 7000 feet, depending upon
how fully developed the spin becomes.

Spin Recovery
Experience has shown that neutralization of all flight
controls will facilitate recovery during the inCipient
phase (uncontrolled flight immediately after a fully
developed stall). Application of spin recovery con-
trols during the incipient phase greatly increases the
probability of spin entry. Therefore, the first step
in any spin recovery is to make certain that the air-
craft is actually in a spin.

The large pitch and roll attitude changes combined
with high yaw rates make it difficult for the pilot to
determine from the outside view whether the aircraft
is spinning erect or inverted. The most positive spin
direction and type of spin indicators are the turn
needle and angle of attack. The turn needle always
indicates the direction of rotation. The angle of
attack indicates whether the spin is erect or inverted:
O-units angle of attack for inverted spin; 30-units
angle of attack for erect spin.
External stores do not affect the recovery procedure
from an erect or inverted spin. Considerable angular
momentum is developed during a spin. Recovery
control application may be required to be held for up
to two turns during the faster flat erect spins.
The control should be held full in the recovery pOSi-
tion until the spin rotation has stopped. Recovery
from even the most adverse spin has occurred within
two turns after proper recovery control was applied
and maintained.

Erect Spin
The recovery technique from an erect spin is brisk
application of full rudder pedal deflection against the
spin (opposite direction of the turn needle) followed
by neutral application of elevator and aileron control
stick deflections. If spin rotation does not stop
within 2 turns, a flat spin has developed. Brisk
application of full aileron control stick deflection
with the spin (same direction as the turn needle) and
full aft elevator control stick deflection must be
applied, while maintaining full opposite rudder pedal
, deflection against the spin, to stop the spin rotation.
Neutralize all controls when spin rotation stops. The
aircraft will be in a nosedown attitude and a diving
pullout should be made to build up airspeed to accom-
plish complete recovery from the spin. An altitude
loss of 4000 to 5000 feet will occur in the recovery.

Inverted Spin
The recovery technique from an inverted spin is brisk
application of full aileron control stick deflection
against the spin (opposite direction of the turn needle)
with simultaneous application of full rudder pedal
deflection against the spin (same direction as aileron).
Elevator control stick position is not critical in an
inverted spin; therefore, a neutral position is rec-
ommended. The ailerons are the primary recovery
control and aircraft response will occur in the form
of roll in the direction of the applied aileron. Spin
rotation abruptly stops as the aircraft rolls around
to an erect nosedown attitude. Neutralize all con-
trols when it is recognized that spin rotation has
stopped and make a diving pullout to build up air-
speed to accomplish complete recovery. A loss of
altitude of 5000 to 7000 feet will occur in the
recovery.

Stabilizer Trim
Stabilizer trim setting will not delay stopping the yaw
and rotation rate of the spin. However, noseup trim
settings greater than approximately 9 degrees may
cause the aircraft to enter an accelerated stall during
dive pullout, subsequent to spin recovery. A stabi.-
lizer trim range of 0 to 4 degrees aircraft noseup IS
recommended. Do not delay applying spin recovery
controls to retrim aircraft.

Dive Recovery
Following spin recovery, airspeed will increase I
rapidly because of the aireraft nose-low attitude.
Altitude loss can be minimized by use of the angle-
of-attack indicator. Smooth noseup elevator should
be applied as the airspeed increases through approxi-
mately 250 knots to attain and maintain 20 units angle
of attack with power added as required to maintain
250 knots throughout the recovery. This will pro-
vide for minimum altitude loss with the minimum
stall margin. Twenty units angle of attack is difficult
to fly without overshooting. Seventeen units or lower
angle of attack is easier to fly and should be used
when terrain clearance is not critical.

 

[jb747]

Back in 1991 there was an accident off the coast of East Sale with a RAAF 707 from 33 SQN Richmond getting itself into a VMCA loss of control scenario at too low an altitude to recover resulting in loss of five lives.

VMCA1 or VMCA2 is a term that comes from the French, and refers to the minimum speed for control, with one or two engines out (on the same side), with take off power set. VMCA2 for the A380 is 144 knots, which is an impressively low speed given the power and moment arm of the engines.

What it means is that if you have asymmetric power (because of an engine shutdown, or demonstration) there is a speed below which the rudder will not have sufficient authority to keep the aircraft straight, so it will start to yaw and roll. During the take off roll, that speed is an abort consideration, as you cannot continue after an engine failure if you don’t have enough to rudder to keep the aircraft straight. It’s VMCG on the ground.

It’s dealt with in the sims, but can be reasonably safely looked at in flight (and test flights have to demonstrate that calculated VMCs are correct).

So, to do it safely in flight...firstly have a reasonable altitude, but it doesn’t have to be in the stratosphere. In the configuration that you’re going to use, slow the aircraft to about 220 or so knots, but well above VMCA. Gently (!) set up the power configuration you want (say two engines at idle, and the other two at MCT). The aircraft will almost certainly start to accelerate, so gently pitch the nose up until you get a gentle deceleration. As it slows you’ll need more and more rudder, until eventually you’ll hit the rudder stops. From that point you won’t be able to stop the roll and yaw, but it will fairly gently roll. At that point the only way to regain control is to balance up the power again, and taking them all back to idle, lowering the nose, and then gently introducing the power again will achieve that.

What you do not do is set the event up by slowing to well below VMCA, and then suddenly introducing the full amount of asymmetric power. In that case the departure will be rapid and violent.

At about the time that this event happened, the RAAF was suffering from a marked loss of its mid level experience and oversight, with airline recruitment having an effect across the board.

 

[RSD]

VMCA1 or VMCA2 is a term that comes from the French, and refers to the minimum speed for control, with one or two engines out (on the same side), with take off power set. VMCA2 for the A380 is 144 knots, which is an impressively low speed given the power and moment arm of the engines.

What it means is that if you have asymmetric power (because of an engine shutdown, or demonstration) there is a speed below which the rudder will not have sufficient authority to keep the aircraft straight, so it will start to yaw and roll.

That sounds like what might have happened here - Video shows private plane crashing into Texas hangar, killing 10

 

[albatross710]

Thank you for the detailed response. Enjoyed reading that. Spent many years at Laverton watching CT4s bounce their way along the strip.

Inverted Spin
The recovery technique from an inverted spin is brisk
application of full aileron control stick deflection
against the spin (opposite direction of the turn needle)
with simultaneous application of full rudder pedal
deflection against the spin (same direction as aileron).

What is the airflow that is giving some authority to the ailerons?

With the A4 flying being on the edge of the envelop, presumably there would be a significant range of power setting prior to an unexpected spin or stall. What is their guidance for power?

 

[jb747]

That sounds like what might have happened here - Video shows private plane crashing into Texas hangar, killing 10

Possibly. It does give you an idea of the rapidity of a departure from controlled flight. I’ll see if I can find the link, but there was a video of an F22 departure, which would have to be the most violent I’ve seen.

 

[albatross710]

Back in 1991 there was an accident off the coast of East Sale with a RAAF 707 from 33 SQN Richmond getting itself into a VMCA loss of control scenario at too low an altitude to recover resulting in loss of five lives.

A while ago I read a review of F18 & F111 losses with the closing remark:

Or maybe the message can simply be put as
has been said before “train like you would fight
but make sure you get to the fight”.

After all, when did Australia last lose an
aircraft due to enemy action?

The document itself is a detailed analysis of accidents and demonstrates the complex environments in which military pilots operate- http://www.pigzbum.com/accidents/sifting-through-the-evidenc.pdf.

 

[jb747]

What is the airflow that is giving some authority to the ailerons?

Where is the air coming from? Well, if it goes flat, probably nowhere, so the recovery is unlikely to work. Generally a spin has some forward airspeed, so there’s some element of normal flow across the controls. Recoveries are not instant, and you might have to sit there, for multiple turns with the recovery controls applied, and nothing seeming to happen.

With the A4 flying being on the edge of the envelop, presumably there would be a significant range of power setting prior to an unexpected spin or stall. What is their guidance for power?

100%. Whilst the power might have been reduced occasionally in an attempt to sucker someone into an overshoot, it otherwise was at 100% right through any fight. You’d pull until you hit the g limit (which varied, but peaked at 7.2g), or until you hit the judder, which is the shaking the aircraft experiences when right on the edge of the stall. In these high g, accelerated stalls, judder is quite violent. With practice you became quite adept at holding it right on the edge.

Because of the slats, the A4 had two phases of judder. As you increased the g loading, it would start, but then as the slats extended, the judder would stop. You could then continue pulling through to the slats out judder, which was as much as you could get. Because the g was mostly applied very rapidly, and often whilst simultaneously applying a roll input, it was possible for the slats to extend asymmetrically. To correct that, you had to rapidly release the g, but if you were losing the fight, it could sometimes work to simply go with it, as the subsequent roll rate actually exceeded the already extreme rate that the A4 could produce (about double the F18s).

 

[flyer89]

I’m fascinated by fighter jets primarily because they are such a foreign concept to me. Were they difficult to fly per se or was it the tasks and speed at which things happened that posed most of the challenge?

 

[jb747]

A while ago I read a review of F18 & F111 losses with the closing remark:
The document itself is a detailed analysis of accidents and demonstrates the complex environments in which military pilots operate- http://www.pigzbum.com/accidents/sifting-through-the-evidenc.pdf.

Most interesting reading. One was even a student of mine at 1FTS.

It gives some idea of the complexity of military flying, and whilst risky, shows why you can’t fly them like airliners in peacetime, and suddenly switch to military mode when war (often with limited notice) appears. When at war, the margins which are discussed as being minimal, would be pushed even further. For instance, in the A4 world, we used to fly maritime missions at 50’ above the water. The Argentine crews attacking the Royal Navy were down at 10-20’.

 

[jb747]

I’m fascinated by fighter jets primarily because they are such a foreign concept to me. Were they difficult to fly per se or was it the tasks and speed at which things happened that posed most of the challenge?

They have become progressively easier to fly, but more complex to operate. Many of my friends flew the F18, and I’ve never heard any describe it as hard to fly, but bear in mind that they all came to the Hornet from either the Mirage or the A4.

The fighters of the ‘60s could be a handful. That’s the era of the Mirage, A4, F4, and F104. They took no prisoners, often had extremely high approach speeds, and nasty high angle of attack behaviour.

But, you didn’t get to any of them in a hurry. All had lengthy programs on aircraft with gradually increasing performance, until you reached them.

You get used to the speed. A minute is still a minute...it’s just that you’ll cover 10 miles during that minute.

 

[flyer89]

They have become progressively easier to fly, but much harder and more complex to operate. Many of my friends flew the F18, and I’ve never heard any describe it as hard to fly, but bear in mind that they all came to the Hornet from either the Mirage or the A4.

The fighters of the ‘60s could be a handful. That’s the era of the Mirage, A4, F4, and F104. They took no prisoners, often had extremely high approach speeds, and nasty high angle of attack behaviour.

But, you didn’t get to any of them in a hurry. All had lengthy programs on aircraft with gradually increasing performance, until you reached them.

You get used to the speed. A minute is still a minute...it’s just that you’ll cover 10 miles during that minute.

Whether true or notI was told the brief and debrief takes significantly longer than Flight you are briefing/debriefing!

 

[kookaburra75]

Extract from the A4G flight manual.
<snip>The aircraft oscillates about all axes in a spin, with erect spins being the most oscillatory. A 360-degree roll occurs during the first one to three turns of an erect spin. Bank oscillations decrease to about 60 degrees after the third turn of an erect spin. The aircraft pitches from near level to a 70-degree nose-down attitude during each turn.
Faster spin rotation rates result in lower altitude loss per turn. Slower spin rotation rates result in greater altitude loss per turn.
Rate of descent will vary from 30,000 to 36,000 feet per minute, depending on the steepness and rotation rate of the particular spin. Load factors of 1. 0 to
3.5g have been experienced during the spin.
Aircraft pitch oscillations vary from 25 to 50 degrees nosedown and oscillations vary between 20 degrees left and right wing down.
</snip>
WARNING
If an inadvertent confirmed spin occurs below 10,000 feet AGL, eject. Recovery from a fully developed spin below 10,000 feet is considered doubtful since 5000 to 7000 feet are required to complete recovery with proper application of the controls.
Recovery from an inadvertent incipient spin may be accomplished with altitude losses varying from 0 to 7000 feet, depending upon how fully developed the spin becomes.

I'll preface this by saying that most of my flying experience in in gliders. As an instructor we'd take pupils through spin training/recovery and look at maybe 500-700 feet for recovery, and at worse maybe 30-45deg nose down. The thought of an aircraft flopping around all around the place in a spln, while dropping at 30,000 feet per minutes and pulling up to 3.5g - it would make me spill my martini in the back seat

 

[RSD]

Possibly. It does give you an idea of the rapidity of a departure from controlled flight. I’ll see if I can find the link, but there was a video of an F22 departure, which would have to be the most violent I’ve seen.

Geezus! That looked a handful!

 

[tgh]

otoh kookaburra, we spun regularly and recovery became instinctive.

 

[jb747]

otoh kookaburra, we spun regularly and recovery became instinctive.

Many aircraft have benign spins. Some will stop the instant the pro spin controls are neutralised, whilst others will take a couple of turns with full anti spin inputs. And still others will respond if they feel like it, and can even go as far as changing from the erect to inverted form, and back again. There’s a reason that drag chutes are fitted to aircraft when the test pilots are intentionally doing test spins.

The Macchi was a nice erect spinner, but a very nasty inverted one. It could fairly easily enter an inverted spin from a slight mishandling of a stall turn. When spinning, we’d take it up above about 20,000’ and spin it down to 12 or so. When the spin stopped, your inner ear was totally mucked up for a short period, and your eyeballs would ‘flick’.

Aircraft designs differ dramatically with regard to where the mass is placed. How heavy/long are the wings, and the same for the fuselage. That gives something called the B/A ratio, which is an indication of the moment of inertia of the wings relative to the fuselage. Some reading here: B/A ratio

Now we get to another joy that the fighters can give, but which is unheard of in other aircraft types. Inertia coupling. This was quite evident in the A4, and was a reason that full aileron deflection rolls were limited to 360º... which was about .5 of a second.
Inertia coupling - Wikipedia

 

[QF WP]

Recent Mayday at Jandakot airport (a Cessna 152 on Saturday 31st August). Second part still to be released. Max is a lucky lad:

 

[QF WP]

Second video loaded up.

The ATC guy was getting on my nerves with his long winded transmissions and over-doing the commentary about how Max (he student pilot) was flying.

 

[QF WP]

Most interesting reading. One was even a student of mine at 1FTS.

It gives some idea of the complexity of military flying, and whilst risky, shows why you can’t fly them like airliners in peacetime, and suddenly switch to military mode when war (often with limited notice) appears. When at war, the margins which are discussed as being minimal, would be pushed even further. For instance, in the A4 world, we used to fly maritime missions at 50’ above the water. The Argentine crews attacking the Royal Navy were down at 10-20’.

The outcome when military training goes sadly wrong - FA18E crash in a canyon used for training (near Death Valley). Truly is a great explanation from Juan Brown and some great video of training in action from 3:25 -

 

[straitman]

CT4 could stalled without restriction. Stabilised erect spins were banned, but the definition of stabilised let you spin it for a few turns. Inverted spins were banned in all types by the RAAF, with the exception that low level display pilots were to be proficient, if it could be safely done in their aircraft. CT4 had an oscillatory erect spin, that could become flat, and so was considered dangerous. Its inverted spin was fast, stable, and quite disorienting.

Macchi was unrestricted for stalls. Erect spins were lovely, and not restricted. Intentional inverted spins were banned, and dangerous. Both RAAF and RAN lost Macchis from inverted spins.

These are good examples of how things evolve with time and experience.

When I did pilot course inverted spins were allowed dual but not solo. They were banned whilst I was still on course.

Initially the CT4 was allowed to do erect spins but occasionally they would flatten out and several people had difficulty in getting the aircraft to respond to the spin recovery. Left hand spins were the worst and I have actually had one that flattened right out and the propellor stopped. Fortunately the recovery was uneventful. About that time the erect spin was banned and it was incipient only as jb747 pointed out.

 

[straitman]

Now we get to another joy that the fighters can give, but which is unheard of in other aircraft types. Inertia coupling. This was quite evident in the A4, and was a reason that full aileron deflection rolls were limited to 360º... which was about .5 of a second.
Inertia coupling - Wikipedia

The RAAF lost several mirages and pilots due to Inertia (or roll) coupling.