Aviation Mythology and Misconceptions
 

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I thought I would start a thread on the erronious ideas that some professional pilots have. See how it runs, it might be interesting.

I will start it off with the argument from someone on this forum that you can do an ADF approach without an ADF. In short, he had misread the FCTM for the Boeing 737. But he may be a trainer - who knows. My answer was as follows:


Sorry, but you cannot do an ADF approach without an operating NDB and ADF - period !

If you do not have a ground station and the appropriate cockpit instrument, you are doing an RNAV FMC approach, not an ADF approach. And we have no RNAV approach plates in our Euro-Jepps, and so I'm presuming that RNAV (FMC/GPS) approaches are not yet certified to any of the airfields we visit in Europe.

Your reference in the 737 FCTM is referring to whether "raw data" or "map display" is selected - not whether the ADF is working or not. In other words, you can use map display mode, if you have overlaid VOR or ADF pointers for cross-checking (which many systems can do) or you flip between raw data and map display to check that the map is in the right position.

Note the note at the bottom of this section: - "Compare VOR and ADF systems to detect possible map shifts". You cannot do a map cross-check, if the VOR or ADF is u/s or not fitted !!


The 1996 Croatia USAF CT-43 crash is what happens, when people use a (map-shifted) RNAV FMC approach, instead of the raw NDB/ADF.


Ditto the B-Med Airbus going into Addis Abeba. The FMC plot and terrain display were off by some 3 miles, leading to a go-around just 60 ft over the high terrain. Now while the VOR would give occasional signals of its unreliability (the VOR was the primary fault), the FMC gave no indication that it had a map-shift. This was the biggest complaint in the report, that the FMC knew it was getting bum VOR information, and therefore may have a map-shift, but did not bother to tell the pilots. And the pilots could not check for a map-shift, because they were comparing bum data with bum data.


The map-plot indicated that the crew were highly influenced by the map and terrain display (rather than the VOR raw data), which showed them passing nicely through the valley. However, the terrain display was likewise mapshifted, and they were 3 miles north of the true inbound. If they had been following an erroneous and displaced VOR radial, it would have eventually taken them to the VOR, whereas this flight paralleled the VOR inbound, which is what would happen if you followed an erroneous FMC position on the map display. Which is why we do no do FMC approaches, especially when we do not have GPS input.

And I am not even sure that GPS-RNAV is entirely a solution at present (as was recommended in the B-Med report). It works well with high accuracy and reliability, but Europe is still concerned that the US may degrade GPS signals or switch the system off during periods of international tension. This is the primary reason for Europe developing and launching the Galileo GPS system. When that is up and running, and there is full confidence that erroneous signals can be detected and warnings given, then Europe may proceed to RNAV approaches.

Just a couple of myths I can recall in 15 secs:

Modern pax transport aeroplanes are capable of reaching coffin corner.

Mach stall exists.

FMS computed position obviates the need for brain computed one.

More experienced pilot is safer and v.v.

"Handling the Big jets" is obsolete.

FBW changes the aerodynamic behaviour of the aeroplane.

FBW is part of the autopilot.

You can not handfly an FBW Airbus in normal law.

With EFIS there won't be partial panel flying anymore.

EFIS display is basically digital.

Speed and altitude tapes are difficult to read.

With FMS taking VOR, DME, GPS, ADC and IRS inputs, there won't be map shifts anymore.

Turboprops are easier to handle and operate than jets.

Since, IAW our Mammonist doctrine, money spent equals dedication, sorting out merely hopeful from truly dedicated is best done by overpricing CPL training, making prospective pilot pay for type rating and topping it off by selling time in RH seat during normal pax ops.

What we read in "Fate is the hunter" is not applicable to modern airline ops.

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As for Dubrovnik and Addis Abeba, what I recall is a slightly (an I really mean slightly) at odds with what you posted, I'll check my references and get back on it later.

I was involved in a "Spirited' discussion here a few year ago with a Military pilot who fervently believed the "Killer Down-Wind Turn" myth!!

And then there's the myth that a B747-400 with one engine inoperative is precisely as safe as one with all 4 running properly.


Edit:

'Ere we go again. If the Mods want to kill it I won't be offended. Doesn't alter the fact that it's a myth, though.

A number of odd ones encountered in very recent years

Myths-
Reduced thrust takeoff is for fuel savings

Temperature of fuel has no effect on volume uploaded

VS is safer than VNAV. (statement: VNAV is dangerous. Do not use it, use VS instead)

QFE Meters is the same as QNH feet

A professional pilot is one who safely busts MDA and finds the airfield in fog
:D

Silver,

"Sorry, but you cannot do an ADF approach without an operating NDB and ADF - period ! "

There are jurisdictions where the overlay approach IS automatically authorized with an approved GPS-FMS navigation system.

Not an absolute rule.

I meant to post "Pilots don't understand difference between RNAV overlay and underlaying approach" but I'm having second thoughts. I'm not sure it's a myth anymore.

Never heard of this one. Methinks original myth was "It is under no circumstances safe to cross the pond on three out of four engines"

737NG approach speed has been increased due to fuselage length(-800 models).

Turning into the 'dead' engine is dangerous.


Forgot about the previously mentioned 'dangerous downwind turn'. :ugh:

"Wow, your a pilot - you must earn loads of cash"

Biggest non-pilot mis-conception ever there.

An old, old myth
 

Passengers will never choose to fly transoceanic on less than four engines!

It was on 707s!

The published VMCA figures increased by 20kts with wings level and we only had one hydraulic system running the Rudder boost. If you lost that - the VMCA increased by about 60 kts.
(See accident report for B707 base training accident Prestwick Airport in 1977)

Edit should be "VMCA figures increases by about 40 kts wings level"

I can't wait to see this one explained.

Hi Clandestino,

Then wait no more. See Page 20 para 2.4

http://www.aaib.gov.uk/cms_resources...8%20G-APFK.pdf

All pilots are treated with a great deal of respect.

There is one for you, as someone else already posted the one about being paid a great deal of money. :p

Then there are the old jokes.

"I wish had as many affairs on the road as my wife thinks I do."

"I wish I made as much money as my wife spends."

"I wish I had as much time off as my neighbor thinks I do."

Feel free to add more. ;)

Thanks Rudderrudderrat! It makes perfect sense :ok:

So turning into dead engine actually is dangerous on the highly-swept-winged aeroplanes with indifferent rudder and 5° bank into live was not just drag reducing measure as I was taught but necessity to get a certain aeroplane certified with low enough Vmca.

EDIT: That would be another myth busted:

Creatively interpreting the certification criteria to effectively bypass them is Toulouse specialty.

You can only land on grooved runways in the wet.:hmm:

SGC

#1 Jet aircraft do not exceed Mcrit in normal operations.

#2 Long Range Cruise speed is the speed for minimum fuel burn.

#3 Best Rate of Climb speed provides the best sector fuel burn.

Regards,

Old Smokey

I'm astonished we've got this far down this thread without the biggest myth of all...

Safety is our first priority

(by the way, you don't need swept wings to make turns towards the inoperative engine hazardous, though I've only found it a significant problem on pretty ancient aircraft)

How about airline pilots are millionaires and all they do is sit there and push buttons all day because flying now is "automatic"?

Wizofoz and downwind turn
 

Just you try the difference between a downwind turn and an into wind turn when you are near enough to the ground to detect it, i.e. on a hang glider.
Its no myth. Its all about energy states between aircraft and ground.

I think the highlighted part of that myth is most dangerous when believed by those who are airline VPs because Daddy was a millionaire and bought them a Harvard or LSE MBA.

One of my favourites:

If an aircraft is not moving (stopped on a taxiway for example), then its not producing any power.

One of my favourites which is particularly prevalent in corporate aviation - the suit at interview glibly announces

"in our company, safety is our absolute priority"

- then they make a derisory daily freelance offer contingent on you first paying for your own type-rating, ditching training, fire-fighting certificate, hazardous cargo certificate, and annual recurrent, and be available 24/365 at one hour notice, and then add that if you don't accept the conditions, there are "plenty of others who will"....

hawk 37

One definition of Power is that it is the 'rate of doing work'.

Work = Force x Distance

If the aircraft's engines do not apply their force (thrust) through a distance, then no work is being done. Ergo, no power is being produced.

(To be honest, I've never heard this 'myth' being expounded anyway, but then I should get out more...........)

Sorry, wilyflier, in a steady wind there is absolutely no difference in aircraft performance - only a visual "illusion" of slip or skid/speed increase or decrease (and it is the illusion which increases the closer to the ground you get). The aircraft neither knows nor cares what the ground is doing until it is forced to interact with it. ;)
Love it :)

Youngsters who love flying (nowadays) think they'll satisfy this desire and become an airline pilot. (Better to get another job and become involved with an aerobatic/tourer.)

Eckhard

Assuming the generators and hydraulics are operational, there is power on a stopped jet. Small point :O

GF

Or an antique! :D

Please explain what you mean.

Obviously the mass of fuel and hence the total calorific content of the fuel per unit volume will vary with temperature. Are you making assumptions about the fuel measurement, i.e. the bowser's flow measurement device also takes account of fuel density, or the aircraft's fuel quantity indicating system is making an adjustment for fuel density?

Apart from the actual expansion of the aircraft fuel tank with temperature, its volume will stay the same. The volume of fuel that can be put into it will stay the same if we assume no tank expansion, but the mass will depend on fuel density.

Eckhard,

Heat energy, and kinetic energy (exhaust) come to mind.

Power plants use turbines to produce electrical power, however of course, like the stopped aircraft, the power plants are not moving.

I'm sure the quote/myth is really meant to mean "there is no power (ie energy) gained by the aircraft" (except possibly warmer brakes).

However I've seen it referred to as "the aircraft is producing no power", clearly incorrect.

Hawk

Conveyor belt, anyone?:ugh:

Killer downwind turn.


This one came about because of slow-speed aircraft turning downwind shortly after takeoff, while simultaneously climbing through a stiff wind gradient. Obviously the climbing into a tailwind will decrease your airspeed, resulting in a possible stall (and the turn itself will further degrade your speed).

Likewise, another glider hazard is the 'clutching hand' effect of descending to land and transiting from a stiff headwind into a nil headwind area (over the top of trees, for instance, into the calm region in front of the trees). As soon as you lose your headwind, you lose your airspeed and drop rather rapidly (feels like a hand dragging you downwards).

But obviously if there is no wind gradient, the windspeed and direction is irellevant to your flight control.

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"Daddy was a millionaire and bought them a Harvard or LSE MBA. "

If my Daddy had offered me a Harvard or an LSE MBA I would definitely have chosen the Harvard.

In hindsight, my comment was made too simply. I should have included, volume required.

Exactly this-
We need fuel by mass, despite delivery by volume. I flew with a fella who had difficulty accepting density values. When I tried to explain to him, it went straight over his head. His 'assumption' generally being that there must be more fuel on board, despite what the gauges say, because the book says the tanks hold x lbs.

I hope that makes sense.

oxenos :ok::ok::ok::ok:

(that's how I read it too!)

Shiny side down, Thanks for the clarification

Thank God windspeed has nil to do with lift. Wind shear is a lie. Does it matter then, if it is the a/c or the airmass doin' the turn?

I think elapsed time has sumpin' to do with it?

the turbulence penetration speed protects you from everything :uhoh:

downwind turn
 

Sorry checkerboard
I doubt you have spent any time doing such manoeuvres in a low mass aircraft with a high wind speed and airspeed ratio, where it is obvious.
Its NO illusion
The visible effect is that you have to lose height as you turn downwind or your airspeed decays.
Even more noticeable is how suddenly you regain that airspeed and height as you turn back into wind
There is another factor involved which could explain it, but I'll leave that for you to find out from your gliding experience

Strata,
(I think you got your take-off wind gradient inverted)
Sorry, forget I said that, I misunderstood that you were climbing through gradient on take off, but actually you referred to wind gradient climbing down wind. In the cases I quote the aircraft were descending downwind, no engine power
Funnily enough I detected the biggest changes occur During the turn , not once youve settled straight downwind

Wilyflier, You could be doing your downwind turn through some hilltop rotor, or getting your inboard wing into lower, slower moving air. The wing only 'sees' the air surrounding it. As you can see the ground directly beneath you from a hang glider, it is very difficult to avoid slowing the glider down as the ground rushes below at a rate of knots.

Sliverstrata is correct in saying that climbing into a tailwind can decrease your airspeed. It is the same effect as decending into a headwind,only the wind gradient is has the opposite direction as your height changes.

If you watch, from the ground, a free flight model aeroplane circling, as it drifts downwind, it will appear to slow down as it turns into wind and speed up as it turns down wind. If you were to observe the same model from above, for example, from a hot air balloon, it would appear to fly a perfect circle.

eckhard
 

If you were to stand behind a running engine, you could test if really no work is produced.