" How I Almost Destroyed a £50 million War Plane...'
 

A friend emailed me this link thinking I'd be interested. Thought I'd post it here for others to read also.


About "Normalisation of Deviance", or departure from SOPs, self-inflicted culture change and deterioration of safety nets.




How I Almost Destroyed a £50 million War Plane and The Normalisation of Deviance. - Fast Jet Performance

Another one is: 'I've always done that but do I really have to; would it make any difference if I didn't?'
That's when you find out that all the little safety bits you've built up over the years work and you start dropping them at your peril.

Normalisation of Deviance
 

Very good article.

Applies to us blunties too and is part of the mandatory HF training we carry out.

It can be interesting being fairly "new" to an organisation and taking a little step back and observing just what is going on....

Excellent article that many of us can relate to I am sure.

Although this "I know better" culture is gradually being filtered out of airlines, it still exists, and in less "regulated" environments, I am sure it is still rife.

You have to be a bit careful with statements like that, because though completely true, that is not necessarily a good thing.

"I know better" is also known as "airmanship and captaincy"

ie If all there was to being a good captain is knowing and following the rules religiously then an autistic pilot with an eidetic memory would be brilliant.

Captaincy and airmanship are all about knowing when the SOP is wrong for the situation.

That requires an "I know better" attitude.

So yes, airlines are losing the "I know better" attitude.

Great article, as well as some of the others on the site!

In the late eighties I was a young Harrier mech and flying a jet with this sort of mechanical discrepancy was unheard of in our organization. The jet would have been grounded, it may have been authorized for a one-time flight with the gear pinned down. If need be the squadron would fly the part out from home base or a different jet.
Interesting story though, the on deployment get'er done mentality can bread all sorts of "normal deviancy"if left unchecked.

Indeed an interesting story. It's been a long time since I flew single seat jet, but I can't help but think I might have gone inverted and tried the negative G heading away from the hard stuff rather than pointing at it....

I think it was zero G.

Difficult to get that without a ballistic trajectory....

Tourist,

point taken, but, as per the original story, I was thinking of making it up as you go along, rather than utilising imagination/experience to get you out of a dire situation.

I am no fan of the "SOP MONKEY" mentality that seems to have become the modus operandi in one particular large loco, where visual approaches are frowned upon, well, unless accompanied by some convoluted "double brief". I am thinking more in terms of the days when FO's had to remember 20 different sets of SOP's to suit the 20 Capts they flew with, some of which were thinking perhaps a little too far out of the box for everyones well being.

how much for a SR-71
 

Here is another from the confessional :

Speed Is Life - Plane & Pilot Magazine | PlaneAndPilotMag.com

Deviance normalised by fast recall of basics of staying aloft, never mind the G`s, the gear or anything else. Thrust is a must.

I agree with Stone69 - inversion was a much better option.
Thread drift warning!
As a very junior Flight Test Engineer some 40 years ago I needed a -1g/M1.0/1,000ft test point The senior FTE looked a my proposed push to -1g and said "not sure the pilot will like that too much, lets just roll inverted and get a gentle push up" Test point achieved every one happy

I haven't flown fast jets and not done that much aerobatics, but could they not have climbed up into the 10s of thousands, above the cloud (or even in the cloud with radar separation) before attempting a level outside turn pushing constant -ve G around the turn until it's up and locked?


Not that they should have done that either, but it strikes me as a safer option than diving at the ground

Some misunderstandings here.

1. There is no need to "gently push up" once inverted to get -1G. You are already there just by being inverted.

2. As stated, the nature of the problem required zero G, not negative G. -1G would be just as bad under those circumstances as +1G.
0G can only be achieved in a ballistic path (or at a legrange point, but that would be very tricky to achieve under these circumstances!)

3. "I haven't flown fast jets and not done that much aerobatics, but could they not have climbed up into the 10s of thousands, above the cloud (or even in the cloud with radar separation) before attempting a level outside turn pushing constant -ve G around the turn until it's up and locked?"

Their idea was misguided.
Yours is insane, and shows a little lack of understanding of G.
Why turn? What is the added benefit?

To get the -ve acceleration, but having re-read it I misunderstood as I thought I'd seen below 0g but actually was under (at) 0g.

My bad for skim reading.

If you were inverted, level, and activated gear up, would the gear not fall into the gear bay & lock under gravity?

No Go
 

"Important' event or not, I would not have flown that airplane on other than a low, slow ferry and with pinned gear, en-route to a Mx base. No!

Thank you for letting us know.
We will all rest easier knowing of your wisdom.

I fear (or she) had completely missed the point of the (rather excellent, IMHO) article.

Tourist, there are indeed some misunderstandings on here. You do not get -1g simply by rolling inverted. You have to remain in level flight to achieve that. But I don't have a monopoly on wisdom, so please feel free to give me the benefit of yours so I can rest easy as well.

Yes you do.
Simply rolling inverted gives you exactly -1g.

Doing anything else does not, i.e. not remaining in level flight.


I can make this easier for you if you want, but I thought the phrase "simply" was clear enough.

Here goes.

Roll inverted.
Don't do anything else.
Don't apply full left or right pedal.
Don't change the power setting.
Don't deploy speedbrakes.
Don't deploy flaps.

Just roll inverted and continue to maintain non accelerative flight with reference to the mean surface of the planet you are currently orbiting.

At this point the only acceleration you are experiencing is the acceleration due to the local gravity of the position you are in. This is generally considered to be a constant of approx. 9.81m/s2 on the surface of planet earth with obvious local variations for velocity of aircraft, position and height on planet earth and as affected by our orbit around the sun and the moons orbit around us.
We call this 1g, or in the event we are discussing, -1g due to the orientation of the aircraft




Personally I think my first statement covered the relevant facts and was more succinct.
If you want any more clarification, please get back to me.:ok:

If you roll inverted and wish to maintain level flight you will require to apply more thrust - unless you have a symmetrical aerofoil with a zero angle of incidence.

Not necessarily, but good general point.

I should have said apply the correct amount of thrust to maintain speed.

To Tourist.
 

Why was Basil's statement not necessarily correct Tourist? Please explain.

Because depending on the aerofoil and angle of incidence, it is possible that you would have to reduce thrust.

Come on, keep up.;)

As Tourist points out, any non-accelerative (constant-speed vector ) trajectory will give you constant pilot-relative 1g. You can then choose to apply this 1g in any pilot-relative direction you want by rotating the plane into any acceptable attitude.

Presumably vectored thrust fly by wire aircraft can maintain very strange constant-speed-vector attitudes, in the same way as powered aircraft can maintain constant-speed-vector attitudes quite different from gliders.


Edmund

back to tourist
 

Err...but as basil pointed out, in the case of a symmetrical airfoil, with zero angle of incidence, that is not the case. So I ask again, why "not necessarily" in response to basil's post?

Ok, I'll try again.

It is possible, would you agree, to have an asymmetric aerofoil that has superior efficiency inverted than the right way up. It is also possible to mount a wing with an angle of incidence giving reduced drag inverted.

Under both or either of those circumstances, it is possible to have a reduced thrust requirement inverted than the right way up.

Not likely, but possible, and in the realms of this "aeronautic basic concepts shlong measuring" debate which we are all involved in, possible is plenty.

Hence "not necessarily, but good general point"

As I said, come on, keep up!;)

There are 2 reasons I find this 'story' a load of bs,
A- no engineer would suggest this solution unless it was a one off rtb.
B- surely select the gear count to ten before going negative g would be a far smarter solution or as suggested inverted flight before gear retraction.

Point A is a fair point.
Point B is another misreading. It was zero not negative they wanted.

How about just doing the whole maneuver in IMC(if you decide to do the maneuver that is).

No you are not.

The aerofoil (or for what matters the entire airframe) doesn't know what's up and what's down as long as the entire contraption is flown straight and lever at constant speed (for relatively short distances the said planet can be considered flat). Drag might be different but that's already another story.

+ or - are mathematical conventions, depending upon the referencing system one's choose. Since weight is a "standard" force experienced by everything on earth, it has been chosen to be positive, perpendicular to the surface and directed to the centre. Wanna go zero-g or negative? Get high the push down sharply...

PZ :rolleyes:

Up from Down
 

True- but what is missing from this ' erudite' discussion is the concept of up versus down.

For a standard airfoil - it is shaped such that the ( lift vector ) in normal flight is UP which allows the plane to fly level and generally at right angles to the gravity vector ( DOWN ) in normal flight. When the two vectors ( lift versus gravity or UP versus DOWN ) balance- the plane flys level at some elevation above local earth.

BUT if you turn the same wing inverted or upside down , then the LIFT VECTOR ADDS TO THE GRAVITY VECTOR, and absent some other forces the plane will go down, still in level flight -at least for a while.:ugh:

Keep in mind that I am talking steady state conditions- absent any other control manipulations or forward vector changes in speed- momentum which can delay the result net DOWN for a while.

You don't have to remain in level flight. Rolling inverted and maintaining the pre roll power setting and airspeed will see the aircraft accelerate into and establish a fixed rate of descent due to increased drag (symmetrical airfoils aside). Once the steady state inverted descent is established -1 "g" will be experienced. Accelerating to the steady state descent will see >-1 "g", -.8 as an arbitrary example.

That's exactly right, and that is why when doing a quick aileron roll, you find the aircraft accelerating downwards at nearly 20 m/s2 during the inverted phase.....

....oh, wait.

Not really true if we are using the aircraft as the basis of what is up or down re g.

As the angle of descent increases, the g relative to the plane of the aircraft's usual up or down drops to zero as the aircraft reaches the vertical.

ie gravity will be pulling directly towards the nose once vertical so zero g relative to gear going up or down.

Sorry, that is badly explained, but I hope you understand what I mean.

I am told that test pilots sometimes do test in an angle of descent for specifically this reason to get less than one g with respect to the aerodynamic surfaces etc despite being in a steady state.

Despite the drop in negative g experienced by the undercarriage due to a descent, you could bring that negative g back up to -1g by throwing in a turn.

interesting ,

I always thought I'd have -1G as I am pushing the stick to stay at level while inverted.
Pushing the stick further gives -2G or more (but then I am not flying level anymore) up to e.g. an inverted loop with -3G up to -4G.

That's the way I explained the -1G inverted in the simplest terms , still correct I hope :8 ?

The fact that if you build a symmetric aerofoil aircraft with zero angle of incidence it is possible to have zero trim change inverted suggests that the push is not what is giving you the negative g....

yep , convinced ...

Missing the point?
 

Am I the only one who is bemused that the folks posting here seem to have missed the point of the article? I'd call it a classic I Learnt About Flying From That (ILAFFT) piece. Normalization of deviation, Human Factors etc. just saying...

BBK