Ex-SAA pilot with 100% safety record died because his passenger was too heavy

[RedAndWhiteBaron]

and an established instructor flying with a new student would automatically have it at front of mind to make sure the aircraft wasn't overloaded.

Culture.

Which also got completely fucked up by the pandemic.

Mmmhmm. You flew overweight because ... COVID.

No - procedures and policies were not in place because we had a bad year. Again, it's not an excuse, but it's a reason. Don't kid yourself, you are not above such a mistake.

[photofly]

I’ve made more than my fair share of stupid and dangerous mistakes. I don’t write about them in public though.

[TG]

Ex-SAA pilot with 100% safety record…

100%
100% safety record up until you run out of luck or get caugh.

[Beefitarian]

I’ve made more than my fair share of stupid and dangerous mistakes. I don’t write about them in public though.

Aww, just write up a couple. It’s fun.

[AirFrame]

I’ve made more than my fair share of stupid and dangerous mistakes. I don’t write about them in public though.

You should. You'll get a lot of stupid comments (or maybe, comments about you being stupid) but interspersed with that will be some great advice from people with thick enough skin that they don't mind wading into the discussion. Ignore the chaff, and take away the wheat.

The OP has already received some great suggestions here about how this could be mitigated in future. Pre-calculating W&B for the two gliders so you can quickly check a go/no-go threshold beyond which a full calculation is needed. W&B cards that would make the calculation quicker and easier (just thought of this but what about a laminated card that you write on with a dry-erase pen?). And finally, for those who have eschewed the flip phone in favour of something made in year starting with a two, a Google Sheet to do it quickly and automatically before the flight. Any of those would mitigate the problem significantly.

On top of *any* of these solutions though, the OP needs the reassurance that it's okay to say "wait" to the three planes behind you, when you're PIC and don't know that you're within limits. The OP didn't make the decision to change instructors on him at the last second, so it's not the OP's fault that the other planes have to wait.

Or a willingness to push off the line, let the next glider go, and push back in behind them once the calculation is done.

A much bigger question is: Had the OP stopped and done the calculation and found that they were 40 pounds over gross, what would have happened? would the instructor say "it'll be fine, let's go"? Would the OP have hopped in, or stood his ground?

[goldeneagle]

With that said, if the glider was struggling on a mere 40lb over max, I think there was more wrong than just the weight.

Gliders are more sensitive than you think.

Glider is an airplane, just like any other airplane other than the fact it's got no engine. So lets take off the pilot hat, and put on my aerospace engineer hat, do a little basic arithmetic.

The equation for lift is L = 1/2 * ro *Cl *S * V^2

L = lift
ro = air density
Cl = Wing co-efficient of lift, which in itself is a function of the angle of attack
V = Velocity
S = Wing area of the wing in question

In your case, there are a couple numbers we can work with, you have stated at gross weight it lands at 55, gross weight is 1000, but, you flew at 1040

So lets do some arithmetic. We will put L at 1000 for the all up gross case, then for the second case, it would be 1040, which is equivalent to L*1.04
V1 = your gross weight case, 55, V2 is the velocity required to generate the required lift in the second case, the number we will solve for

Two equations come about

1/2 * ro * Cl * S * V1^2 = L
1/2 * ro * Cl * S * V2^2 = L * 1.04

These two equations define the two conditions, so lets re-arrange them a little bit

L / (1/2 * ro * Cl * S) = V1^2
L / (1/2 * ro * Cl * S) = V2^2 / 1.04

Since air density, angle of attack and wing area are equal in both cases, as is the value L, we can now see that the left hand side of both equations is the same, so, we can set the two right hand sides equal to each other

V1^2 = V2^2 / 1.04

which re-writes as

V1^2 * 1.04 = V2 ^2

Solve for V2 and you get

V2 = sqrt( V1^2 * 1.04 )

Plug in your value 55 for V1, and it doesn't matter if thats mph, m/s or knots, units all cancel out in this situation, but I'll assume it's mph for the glider.

sqrt( 55 * 55 * 1.04) = 56.09

So with your extra 40 pounds on board, to get the extra lift required at the same angle of attack as the normal gross weight case that glider has to go a whole 1.09 mph faster. When flying the glider, is your speed control accurate enough to differentiate between 55 and 56 while on a tow? Is the indicator on the glider even that accurate ?

I'll stand by the original comment, if normal is 55 at 1000 pounds, then when you were at 1040 and struggling at 60, there was more wrong than just an extra 40 pounds on board.

Now as an exercise for the reader, what would happen to your airspeed indications if during the previous landing a piece of grass or other debris had ended up in the pitot tube ? What about if it ended up in the static port ? I can certainly see the situation you describe if one is chasing an airspeed number on an ASI that's not reporting correctly.

[youhavecontrol]

Food for thought:
I fly medevac now and I've held up countless departures for the two minutes it takes to ammend the weight and balance when the escort unexpectedly changes or someone needs to swap seats. Held up a labouring mother, burn victims, etc... for THEIR safety.
There's nothing so urgent that it's worth risking a healthy crew and a perfectly good airplane on an assumption.
If the environment you operate in can't cope with unplanned but necessary safety measures, there needs to be a better safety culture and perhaps changes to the format if they truly think a delay is unacceptable.

['97 Tercel]

With that said, if the glider was struggling on a mere 40lb over max, I think there was more wrong than just the weight.

Gliders are more sensitive than you think.

Glider is an airplane, just like any other airplane other than the fact it's got no engine. So lets take off the pilot hat, and put on my aerospace engineer hat, do a little basic arithmetic.

The equation for lift is L = 1/2 * ro *Cl *S * V^2

L = lift
ro = air density
Cl = Wing co-efficient of lift, which in itself is a function of the angle of attack
V = Velocity
S = Wing area of the wing in question

In your case, there are a couple numbers we can work with, you have stated at gross weight it lands at 55, gross weight is 1000, but, you flew at 1040

So lets do some arithmetic. We will put L at 1000 for the all up gross case, then for the second case, it would be 1040, which is equivalent to L*1.04
V1 = your gross weight case, 55, V2 is the velocity required to generate the required lift in the second case, the number we will solve for

Two equations come about

1/2 * ro * Cl * S * V1^2 = L
1/2 * ro * Cl * S * V2^2 = L * 1.04

These two equations define the two conditions, so lets re-arrange them a little bit

L / (1/2 * ro * Cl * S) = V1^2
L / (1/2 * ro * Cl * S) = V2^2 / 1.04

Since air density, angle of attack and wing area are equal in both cases, as is the value L, we can now see that the left hand side of both equations is the same, so, we can set the two right hand sides equal to each other

V1^2 = V2^2 / 1.04

which re-writes as

V1^2 * 1.04 = V2 ^2

Solve for V2 and you get

V2 = sqrt( V1^2 * 1.04 )

Plug in your value 55 for V1, and it doesn't matter if thats mph, m/s or knots, units all cancel out in this situation, but I'll assume it's mph for the glider.

sqrt( 55 * 55 * 1.04) = 56.09

So with your extra 40 pounds on board, to get the extra lift required at the same angle of attack as the normal gross weight case that glider has to go a whole 1.09 mph faster. When flying the glider, is your speed control accurate enough to differentiate between 55 and 56 while on a tow? Is the indicator on the glider even that accurate ?

I'll stand by the original comment, if normal is 55 at 1000 pounds, then when you were at 1040 and struggling at 60, there was more wrong than just an extra 40 pounds on board.

Now as an exercise for the reader, what would happen to your airspeed indications if during the previous landing a piece of grass or other debris had ended up in the pitot tube ? What about if it ended up in the static port ? I can certainly see the situation you describe if one is chasing an airspeed number on an ASI that's not reporting correctly.

Cool story, bro

[RatherBeFlying]

It's really not that hard for most 2-seat gliders:

1. Add your weight with chute to the empty weight and subtract from gross weight to obtain maximum passenger weight with chute when you are flying.

2. Calculate minimum front seat weight if not already on placard. Lighter students will require ballast dual and solo.

[photofly]

With that said, if the glider was struggling on a mere 40lb over max, I think there was more wrong than just the weight.

Who said it was 40lbs overweight? I can't find that reference.

- EDIT - found it. Never mind.