Santulli's visit to SC?

[NJA Capt]

My office is at 51,000 and Mach .92 What's that got to do with it?

Well.....at least until we get these.

 

[GVFlyer]

A Global Express, but bigger. Flown a Phantom II at TPS-a pig by today's standards.

Miles, I have to get involved here. While the Global might out perform a Phantom II, it doesn’t come close to meeting the performance of the G550.

The first reason is simple physics - the G550 weights 7.5% less and has 5% more thrust. The Basic Operating Weight for the G550 is 48,000 lbs and it has 30,770 pounds of thrust giving it a basic power loading of 1 pound of thrust for each 1.56 pounds of airplane. The BOW for the Global Express XRS is 51,500 lbs and it has 29,500 pounds of thrust. Thus the Global has 1 pound of thrust pushing 1.75 pounds of Canadian jet. Of course this doesn’t account for some of the trick stuff on the G550 like the Thrust Recovery Outflow Valve which vectors outflow air at up to 10.48 psid for additional thrust or the blunt edged flap trailing edges which reduce drag above M 0.85.

The comparison is worse at max gross take-off weight – the G550 takes off at 91,000 lbs, the Global XRS has less thrust pushing 98,250 lbs at take-off.


Number two and more importantly is Gulfstream's basic design philosophy. Let me explain. The thrust deck or propulsive power (Wpa) available determines the aircraft volume that can be propelled through the air at a given speed. As such, with the same engines, the volume of the GV and the GEX is roughly equivalent. Bombardier spent more of their volume on cabin, Gulfstream spent theirs on wing. The Gulfstream has 1136.6 sq ft of wing, the Global has 1022 sq. ft. The resultant is that the GEX is a high wing loading, point design, buffet limited airplane and the Gulfstream is not. The Global also pays for this large cabin with increased total parasite drag.

Design limit speed on the GV occured when rudder CL beta went positive (fundamentally a control reversal) not because of buffet or flutter. As a matter of fact, serial number 501 went to Mach 1.07 during developmental test. What this means to you is a much more generous height velocity diagram.

For example, in a 63,000 lb G550 at M.080 at 45,000 feet you can perform a 60 degree (2 g) bank without encountering buffet. With the same conditions in the Global you would encounter buffet at 52 degrees or 1.62 g. In a 55,000lb G550, you can still do sustained 45 degree banked turns at 51,000 feet.

Why this is important is that it gives you a huge window between compressibility and stall at altitude. These margins keep you safe if you encounter turbulence and mean that you don't have to descend if it gets hot. No Gulfstream pilot has ever had to look at a buffet chart to see if he could climb. Performance is paramount at Gulfstream.

My biggest personal beef against the Global line is that it is a buffet-limited jet and does not offer the kind of margins found in the Gulfstream GV and it's derivatives. On the G550 there is over a 100 knot window between compressibility and stall at 51,000 feet. Gulfstream has never departed a GV/G550 during development or any other phase of flight. Pete and his test boys had to pull the chute on the Global to regain controlled flight when it pitched-up during FAA required stall testing.

When we did a closed loop handling qualities evaluation of the Global, we got impending indications of an aerodynamic stall prior to shaker and had to knock it off for the test. The Global actually speeds up in a turn at a constant power setting showing that it is aerodynamically operating in the wrong part of the “drag bucket." We could not get the jet to 49,000 feet with only a crew of two and four flight test engineers on board. The area rule design on the Global, while a good idea on fighters, is a design emergency procedure on a transport category jet to reduce excessive drag.

We also found that Max cruise speed was lower than expected. At FL450 and 65,000 lbs, the cruise manual shows the jet should be able to achieve M 0.87+, the Global could only get to M0.865.

During GV altimetry certification we had to fly close formation at various altitudes with a known source. We used the FA-18 for these tests. After completion of the tests at 51,000 feet, the Hornet driver thought he was going to make a run on us. He quickly learned that the FA 18 won’t turn with a Gulfstream at that altitude…and no, we didn’t use “After Fan” (Alternate N1 Control which gives us an additional two-tenths [!] of EPR).

Miles, I saw that you’re a TPS grad. If you’re looking to get back into that line of work, Raytheon needs a test pilot. They just lost one of their guys to Adam Aircraft.

GV







~

 

[semperfido]

i knew there was a reason i liked this g550 so much (and the gv and giv)

 

[G4G5]

Exactly what I was going to say but you beat me to it.

Thanks.

 

[RTRHD]

WOW, V Flyer I am impressed.

 

[Muddauber]

Nice post, GV. I miss the Gulfstream's performance, particularly on positioning flights.

Muddy

 

[Muddauber]

.........................................................................................................

 

[Spyguy]

Miles,
I have to call you out on part of that statement. The F-4 might be a pig by today's Generation 3 and 4 fighter standards, but you and I both know that it can fly far faster than anything any version of an F-18 can come close to, even in a dive. The F-18 isn't exactly known for its speed. So, the Phantom may be older but it is still "faster" than some of today's jets.


"Go Navy Beat Army"

 

[miles otoole]

Miles,


"Go Navy Beat Army"

Now that's the ONLY thing I agree with.

 

[SeaSpray]

...(referring to an earlier post, where you denegrated (sic) Army Warrant Officers as uneducated and unworthy)...

No, chief, I just denigrated you as uneducated and unworthy. The Warrant Officers I met during my joint service tour were professional officers and technicians competent in their specialties.

You still haven't told me what TurboJet you fly.