How does Elon Musk’s G650 land and T/O on a 4,800’ runway?

kicktireslightfires

kicktireslightfires

Pre-takeoff checklist
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kicktireslightfires
His G650 regularly flies in and out of KHHR, but their runway is just 4,884’ and the G650 supposedly needs 5,858’ for T/O. So what’s going on? Did he install some Raptor rocket engines on it for JATO? I understand 5,858’ is based on MTOW, but even if we assume they takeoff from KHHR with half fuel, how do they make less than 4,900’ work? And aren’t they cutting the minimums dangerously close?
 
I’m sure doesn’t pack it with the maximum number of passengers (18)…probably just crew and himself most of the time.
Add a little wind, but yeah, there’s not much margin for error or engine failure.
 
kicktireslightfires said:
His G650 regularly flies in and out of KHHR, but their runway is just 4,884’ and the G650 supposedly needs 5,858’ for T/O. So what’s going on? Did he install some Raptor rocket engines on it for JATO? I understand 5,858’ is based on MTOW, but even if we assume they takeoff from KHHR with half fuel, how do they make less than 4,900’ work? And aren’t they cutting the minimums dangerously close?
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At what weight does it need 5858’ for takeoff?
 
Take off and climb performance is all predicated on weight, altitude and temp.
You can't change the altitude at Hawthorn, and most passengers don't want to change their schedule to TO in the cooler mornings and you can't kick off passengers, so all you have to work with is weight, which means less range.
 
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I am surprised they can operate out of there on a regular basis with the runway load bearing capacity as low as it is:

Weight bearing capacity:
Single wheel: 30.0
Double wheel: 60.0
Double tandem: 90.0

But, that isn't a strict limit. Easy enough to get permission from the airport manager to exceed that weight. I'm sure a "donation" was made.....
 
MooneyDriver78 said:
I’m sure doesn’t pack it with the maximum number of passengers (18)…probably just crew and himself most of the time.
Add a little wind, but yeah, there’s not much margin for error or engine failure.
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Margin for engine failure is built into the takeoff numbers on a jet.
 
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The G650 can carry enough fuel to cross oceans (8,000+ miles). Remove a bunch of that fuel, so that you have enough to get around the United States, and operating with 4900 ft of runway is no issue at all.

Fuel is heavy. Your 5800 ft number is assuming around 45,000 lbs of fuel. Think about that. It takes TEN Ford F150 trucks to equal the same weight a G650 will have in its fuel tanks when they're full. They're not flying around with 45,000 lbs of fuel on any regular basis.
 
jesse said:
The G650 can carry enough fuel to cross oceans (8,000+ miles). Remove a bunch of that fuel, so that you have enough to get around the United States, and operating with 4900 ft of runway is no issue at all.

Fuel is heavy. Your 5800 ft number is assuming around 45,000 lbs of fuel. Think about that. It takes TEN Ford F150 trucks to equal the same weight a G650 will have in its fuel tanks when they're full. They're not flying around with 45,000 lbs of fuel on any regular basis.
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With 1/2 fuel (3000ish miles) you'd be roughly 75% max gross. Reduce it to 1000 mile range and you're down to 61% max gross.

I have no idea how that translates to runway requirements.

The funny thing is the weight of the people and their baggage is pretty much a rounding error on a craft like that.
 
Probably easily doable if they’re not gassing up for an 8 hour flight.
 
Salty said:
With 1/2 fuel (3000ish miles) you'd be roughly 75% max gross. Reduce it to 1000 mile range and you're down to 61% max gross.

I have no idea how that translates to runway requirements.

The funny thing is the weight of the people and their baggage is pretty much a rounding error on a craft like that.
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In my airplane, reducing weight 25% below max reduces runway by more than a third. I’ll let you do the math—
4406’ to 2783’ on a 20C day at sea level.
 
EdFred said:
I presented the math on this a while back.

Remember V speeds change with weight. So if lighter, lower Vr, Vs. Also if lighter, power:weight is higher. Acceleration rate is faster, braking is better. Takeoff and landing distances are shorter. How is this not common pilot knowledge/sense?
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This is a basic cut at it. Without getting too in-depth, some funny things can happen with takeoff data in big airplanes that you wouldn't expect. For instance, you're mostly right that lighter is going to give you a lower V1, Vr, etc. But there are times that if you get too light, V1 and Vr start increasing again.
 
Sluggo63 said:
This is a basic cut at it. Without getting too in-depth, some funny things can happen with takeoff data in big airplanes that you wouldn't expect. For instance, you're mostly right that lighter is going to give you a lower V1, Vr, etc. But there are times that if you get too light, V1 and Vr start increasing again.
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Sounds like some kinda reverse behind the power curve thing.
 
EdFred said:
Being not type rated in.....anything, what's the reason for increased V1 and Vr?
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Mostly it would be a Vmca problem. Since the plane has mass/inertia that helps to counteract the yawing tendency after an (outboard) engine failure. A heavier plane would resist that more, but a lighter one would be affected more. So, the lighter the plane gets, the faster your Vmca has to be. There will come a point where in order to keep your Vmca below Vrot, you'd actually have to artificially increase Vrot in order to not unstick slower than Vmca.

So, it's definitely a corner case, but I've run into it in the KC-135. With the outboard engines pretty far off the CL, high thrust, light weight takeoffs would sometimes be problematic from a takeoff data standpoint.
 
You can get a loaded C-17 into a 3583' runway, but need to shed some cargo to get back out....
 
Sluggo63 said:
There will come a point where in order to keep your Vmca below Vrot, you'd actually have to artificially increase Vrot in order to not unstick slower than Vmca.
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Technically it’s V1 that has to be above Vmca. With Vr at or above that, the effect is as you said.
 
Even a lightly loaded 747 with a few hours worth of fuel can liftoff with a 1500 foot ground roll, at least in the sim. You can't use part 25 performance criteria to do it though, you simply use a Cessna style short/soft field technique and rotate into ground effect. You're probably going to buy the farm if you lose an outboard motor right at rotation though.
 
Luckily, most of us will never have to worry about our jet being over-weight for a short runway;):confused::eek::p
 
NoHeat said:
It has displaced thresholds at both ends. If those can be used for takeoff, then it’s more.
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And you can use a clearway as well.

The clearway is a clearly defined area connected to and extending beyond the runway end available for completion of the takeoff operation of turbine-powered airplanes. A clearway increases the allowable airplane operating takeoff weight without increasing runway length. Source: https://www.faa.gov/documentLibrary/media/Advisory_Circular/150_5300_13_chg8.pdf
 
Interesting, about a "clearway." That's new to me.

Are there any examples? I searched the Chart Supplement for North Central U.S., and the word clearway isn't in there for any airport.
 
jordane93 said:
Probably easily doable if they’re not gassing up for an 8 hour flight.
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8 hr flight is such a baby flight for the ER. That's at least a 14 hr airplane at max takeoff weight. I'm wondering what the T/O distance would be on a little 8hr hop at sea level and about 80°f
 
MauleSkinner said:
Technically it’s V1 that has to be above Vmca. With Vr at or above that, the effect is as you said.
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Maybe we're misunderstanding each other.

When we ran takeoff data, we had to ensure that V1 (we actually use S1 in the KC-135, slight difference, but essentially the same for these purposes) was greater than or equal to Vmcg. We also had to ensure that Vto (takeoff speed... essentially a few knots after rotate) was greater than Vmca.

To me that all makes sense. If Vmcg was greater than S1, then you could be in a position where you could lose an engine just above S1, by definition are then committed to the takeoff, but yet be below Vmcg which means you don't have directional control.

Same with Vmca and Vrot/to. If your takeoff speed is less than Vmca, that would mean you could conceivably get airborne, but yet be too slow to have directional control with an engine failure.
 
But backing off thrust on the good engine would bring you back under control, possibly with enough thrust to continue the departure.

The examples we are looking at here, the aircraft has a large surplus of thrust, due to the low takeoff weight. Heavier departures would not have the same option.

The sort of decision that is hard to get right, even if mentally prepared for the possibility.
 
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