Attn: Swept Wing Transport Pilots

[AluminumDrvr]

I just wanted to get some comments from some real pilots on an old trick we used to use as CFI's.

We all remember the "felt tip pen" trick used when we show students how to make a coordinated level turn at constant speed in a 152.

But... now i have a guy claiming to be a 747 Capt and that you can use the same trick in a swept wing aircraft.. dutch roll and all, to line up with a target (as in arrival, approach, through to landing) This man believes you can put a felt tip pen mark on your windshield in a transport category airliner and hit his mark every time.. no matter the maneuvering or change in airspeed involved. Here is his quote...

"You sit in the seat, hold the pen out straight in front of you and make a mark on the windscreen. When you bank the aeroplane left and right, all you do is keep that dot on the horizon and the plane will stay level.
But you can also use it to track objects ...
... for example, make the same dot and then manoeuver the plane so the dot is right over what you want to hit, and the plane will hit it, and very accurately."

I suppose this guy doesnt know about crab angles either... or changes in deck angle..

Now we all know the answer to the above quote is pretty much laughable, but i just wanted to get a nice thread of all the laughs for this poser. I hate internet posers.. dont you?

[cwatters]

Originally Posted by AluminumDrvr

... for example, make the same dot and then manoeuver the plane so the dot is right over what you want to hit, and the plane will hit it, and very accurately."

Well in theory that's right. If you keep manovering so that the target is allways on the same bearing you will hit it. You might not take the shortest path to point of impact and there are lots of if's and buts but the principle is sound.

There is a well known trick that sailors use... Lets say you are sailing along and see another boat in the distance going at a different speed that may cross your path. Will you collide? To find out you take a compas bearing on the other boat and sail on for awhile. Take another bearing and if it's the same as the first you probably will collide. Works in 3D just as easily.

[barit1]

In my co-op days I worked on an anti-aircraft missile guidance system - and guess what? That's exactly the guidance logic used to guarantee intercept.

In fact - test missiles were fired at WWII surplus drone aircraft, with a telemetry packet (measuring miss distance) replacing the warhead. I distinctly recall a photo of a B-17 on the ramp with a big gouge in the lower aft fuselage where it had taken a direct hit from the unarmed missile. However the robust B-17 remained in one piece, its control cables intact, and it came back to the drone recovery runway without further damage.

[AluminumDrvr]

You guys are really comparing a swept wing aircraft, dutch roll, deck angles and all... to a boat and/or a homing missle? Is this a joke?

What if you need to maintain 5 degrees pitch up to maintain level flight? You still gonna stick that pen mark on your target? Think you'll hit it? or fall short...

geeze...

[Halfbaked_Boy]

Originally Posted by cwatters

Well in theory that's right. If you keep manovering so that the target is allways on the same bearing you will hit it. You might not take the shortest path to point of impact and there are lots of if's and buts but the principle is sound.
There is a well known trick that sailors use... Lets say you are sailing along and see another boat in the distance going at a different speed that may cross your path. Will you collide? To find out you take a compas bearing on the other boat and sail on for awhile. Take another bearing and if it's the same as the first you probably will collide. Works in 3D just as easily.

It's called 'homing'

Cheers, Jack.

[cwatters]

Originally Posted by AluminumDrvr

You guys are really comparing a swept wing aircraft, dutch roll, deck angles and all... to a boat and/or a homing missle? Is this a joke?

What if you need to maintain 5 degrees pitch up to maintain level flight? You still gonna stick that pen mark on your target? Think you'll hit it? or fall short...

geeze...

Well that's what I meant by lots of "if's and buts". There are thousands of ways it won't work - for example if the target is faster than you and going away or the flight path required exceeds the performance capabilities of your ride in other ways, then it won't work obviously....but the principle is correct.... constant bearing => collision.

[FE Hoppy]

"What if you need to maintain 5 degrees pitch up to maintain level flight? "

At what speed?


I think you will find that the claim is not false!!

[misd-agin]

Originally Posted by FE Hoppy

"What if you need to maintain 5 degrees pitch up to maintain level flight? "

At what speed?


I think you will find that the claim is not false!!

757 at min airspeed for flaps 5 in the arrival pattern is typically 7.5-8 degrees nose up.

The dot would be well above where you are actually flying.

[barit1]

A bunch of people are missing the point. (Bad pun???)

If you keep the dot aligned on the target, using whatever combination of thrust and stick & rudder are required to do so, and if the plane has sufficient performance to maintain this aimiing point...

AND if the target isn't outrunning you...

You will hit it!

[AluminumDrvr]

Originally Posted by barit1

A bunch of people are missing the point. (Bad pun???)

If you keep the dot aligned on the target, using whatever combination of thrust and stick & rudder are required to do so, and if the plane has sufficient performance to maintain this aimiing point...

AND if the target isn't outrunning you...

You will hit it!

The problem here is that the original quote suggests you draw the pen mark on the windscreen, then maneuver your airplane to the target. For example, you write the mark on the windshield outside the marker on an ILS to correspond to the area of the runway you would like to land. He claims that if you keep that spot on the runway, while maneuvering for landing, that you will hit that spot.

The actual maneuver he claims this will work on is if someone put the mark on the windscreen at 7000 feet, then kept that mark on the target 5 miles away on the ground, that the aircraft can descend and maneuver to hit that target through changes in airspeed, changes in wind direction as you descend closer to the ground and/or configuration.

I agree that if you place a mark on the windscreen and keep a constant airspeed and altitude, you can home into your target. The original quote suggest you place the mark, keep the target on that mark, and then maneuver AFTER the mark was placed regardless of altitude change, airspeed, or configuration.


I know full beards are prohibited in the US via the company manual approved by the FAA due to O2 mask seal (it wont form a proper seal with facial hair), but is it prohibited in most company manuals abroad? Regardless if it approved or not... its not very smart to fly a jet with a full beard.

Thanks for the input guys...

[AluminumDrvr]

Originally Posted by barit1

A bunch of people are missing the point. (Bad pun???)

If you keep the dot aligned on the target, using whatever combination of thrust and stick & rudder are required to do so, and if the plane has sufficient performance to maintain this aimiing point...

AND if the target isn't outrunning you...

You will hit it!

Thats not true... what if the pilot placed the mark at 200 knots, and then accelerated to 400 knots in a dive? Clearly if he kept that mark on the target he would not hit it based on the change in angle of attack alone.

[Chesty Morgan]

And the same can be said of a C152. Make your mark at 60kts and accelerate to 120kts you'd miss!

[AluminumDrvr]

Originally Posted by Chesty Morgan

And the same can be said of a C152. Make your mark at 60kts and accelerate to 120kts you'd miss!

exactly..

[Ag2A320]

Whats the big deal about beards, my company allows you to wear a beard with a medical cert from a doctor,(easy to get) requires that you grow it on vacation and even went as far as outlining the grooming requirements for upkeep of said beard in our ops manual. My last DFO & CP both had beards, and we have a couple captains in my current base that have full beards. As for the oxygen mask story, i heard it before, personally have yet to see any hard evidence of a CM passing out during a E-decent or in the chamber, due to wearing a beard, additionally never heard anything from any of the FAA inspectors that have rampchecked me when i had a full- beard at JFK,LAX,ORD,MIA or any other airport(domestic and International). Our ops manual allows for beards on our current fleet A320/321/340 and was approved on the older DC-8/9,B727/B747 fleet.

[Loose rivets]

There was an aviation pioneer called Col Carl Crane, he spent much of his life in San Antonio
Tx. I had the pleasure of flying with him on many occasions when he was nearing the end of his life.

In the ‘old days', he spent a lot of his time making people believe in their instruments; trying to counter the "they stop working when we go into cloud" mentality. He often lectured at Randolph Advanced instrument flying school. Most of his lectures were trips down memory lane...but very exciting stories.

He had several US patents. One of these was a little double cross made of brass. It was called ‘the nose knows.' I guess that the second horizontal was to allow for a change of speed, but I don't know.

[AluminumDrvr]

Originally Posted by Ag2A320

Whats the big deal about beards, my company allows you to wear a beard with a medical cert from a doctor,(easy to get) requires that you grow it on vacation and even went as far as outlining the grooming requirements for upkeep of said beard in our ops manual. My last DFO & CP both had beards, and we have a couple captains in my current base that have full beards. As for the oxygen mask story, i heard it before, personally have yet to see any hard evidence of a CM passing out during a E-decent or in the chamber, due to wearing a beard, additionally never heard anything from any of the FAA inspectors that have rampchecked me when i had a full- beard at JFK,LAX,ORD,MIA or any other airport(domestic and International). Our ops manual allows for beards on our current fleet A320/321/340 and was approved on the older DC-8/9,B727/B747 fleet.

What company do you work for? And what are the guidelines for grooming as to not interfere with the O2 mask? Our ops manual specifically prohibits beards for pilots. FA's can wear them.. but not pilots. One reason is due to the AC below.. (i also have never seen an active line pilot in a beard in any terminal. Although i seen many grow them on vacation.. i do too.. )


FAA Advisory Circular on the Influence of beards, from 1987.

a. Several investigators had reported that the presence of beards
caused a decrement in the efficiency on half masks, full masks, and -.
respirators. A Department of Navy study (No. NADC-722110CS) reported an '
average inboard leakage of 16 to 67 percent for military-type crew oxygen
masks when tested with subjects wearing beards to altitudes of 18,000 feet.
Civilian crew oxygen masks vary considerably from these types of masks
because of differences in basic mask designs, suspension systems,.,and
controlling regulators. Consequently, CAMI conducted'research to determine
if the problems noted in these reports would also be present when civil
aviation oxygen equipment was tested.


.... respirator/oxygen (sometimes
referred to as "demand") masks cannot be donned rapidly and do not seal
over beards or heavy facial hair. This lack of a seal could result in a
reduced amount of oxygen in the mask and the entry of smoke or toxic fumes
that could result in reduced crewmember capability and performance.


...This can adversely affect the performance of the mask and reduce crewmember
awareness, capability, and performance.

http://www.airweb.faa.gov/Regulatory...E/AC120-43.pdf

[FullWings]

I think it is technically correct that if you can keep a dot drawn anywhere on the windscreen aligned with your "target" and the range is reducing, you will hit it. You might have to do some strange things with the controls, however! This applies in whatever configuration you are in as long as you are still closing. If at some stage it becomes impossible to keep the dot aligned, then you're going to miss - that is the whole premise of the argument: a constant relative bearing will lead to an interception...

[TURIN]

Don't know much about the dot on the windscreen bit. My hang-glider didn't have a windscreen!

However, regarding beards. I remember several line pilots operating out of MAN about 5 years ago who wore prominent beards.

Also, I understand that orthodox muslims do fly aeroplanes, beards and all!

[littlejet]

It worked in 727

When you are configured to land just keep the landing TCH of the RWY in the middle of your windscreen and you are on the approx 3 degree path. Same seems to work in 744 but the rwy should be little lower than the middle, but I newer really tried that in jumbo

[Loose rivets]

It used to be that to obtain a US patent, it had to work, or reasonably be expected to work if it had not become a reality. The colonel's little brass cross had been manufactured in small quantities, and I know that it worked.

Comparing with a boat. Well, the same rules apply about a constant bearing, be it plane boat or car.