View Full Version : G-IIB/G-III Question
12th Jul 2012, 20:25
During normal, all engines operating, takeoff (10 deg flap), what is the expected AEO airspeed at 35 ft? Can they make 164 KIAS?
Also, the AFM states that best climb gradient available OEI is always at V2+10. Any significance to the 10 knot difference, given a pre-takeoff V2 target calculation instead?
And finally, how bad is the assymetric thrust effect OEI? Lots of rudder, maybe a slight bank towards the remaining engine?
13th Jul 2012, 19:10
First normal take off is Flaps 20.. immediately after gear up then you go to flap 10 on the 2's and 3's.. On the 4's and 450/550 its flaps 20 take off after gear up it immediately flaps up.
You will fly so fast through V2+10 that is recommended to just maintain what you have for the climb but not to decrease below V2+10, directional control is the most important... Its just like all the other jets out there, just it has more balls single engine than most!!!
Asymmetrical thrust is not more than the rudder can handle.
My two cents
13th Jul 2012, 23:48
noneya, thanks for the help.
First normal take off is Flaps 20.. immediately after gear up then you go to flap 10 on the 2's and 3's..
OK, but 10 deg TOs are also allowed per the AFM, right? "Normal" must be subjective in this case (me thinks). :) Granted, runway length used will decrease at flaps 20, but climb would suffer if not reduced to 10 soon, is that correct?
You will fly so fast through V2+10 that ....
From what I've heard, this is true. IOW, it takes a pretty aggressive rotation to prevent acceleration at 35 ft to greater than V2+10. Do I have this right?
15th Jul 2012, 09:28
Gulfstream recommends flaps 20 takeoffs for all their aircraft. You are correct that, flaps 10 T/O's are allowed, however typically they are only used when you get into a runway performance issue. Such an issue would be: If you are trying to make a second segment climb out of a high altitude airport during a hot summer day, at a heavy weight. When using T/O with flaps 10 you have to be care full with tire rotation speeds and of course runway length.
As I mentioned, the aircraft accelerates so fast, and a flaps 20 T/O gets you off the ground quicker and at a lower speed, that by the time you rotate with a positive rate you are already calling for gear up, flaps 10 (in a GII-GIII) this is all done right after you are airborne. So there really is no down side to taking off flaps 20 as normal procedures, unless of course you are performance limited.
You are also correct about an aggressive rotation to try and maintain V2+10 at 35 feet! As a matter of fact it is so aggressive that in order not to make the passengers uncomfortable, most operators do not try and maintain V2+10 on climb out during normal operations, we fly a much shallower departure, which still in most cases is greater than 2000/2500 ft per min. This again is why I said if you lose an engine after T/O you can always start your pitch to V2+10 but there really is no reason (unless you have terrain) to get that slow.. Directional control is more important than to try and following a book number airspeed, the plane will climb!
Let me follow this all up by saying! Follow the recommended Gulfstream procedures for flying the plane. That is always the best procedure.
Once you have time in the plane you will find what you and your passengers like best!
Enjoy the plane, it is one of the greatest planes ever built!!!
I have flown the GII, GIIsp, GIIB, GIII D/C and A/C, G-IV, GV, G450, G550 and I would have to say for me (in pure fun to fly) the GIIB was my absolute favorite aircraft to fly!
Hope this all helps in some way!
16th Jul 2012, 00:49
Hope this all helps in some way!
noneya, it absolutely does! Thanks very much for that summary, I've learned a lot. :D
One final quick question, if it's OK: The AFM calls the RIGHT engine the "critical engine". Why would that be? A cursory systems review of the II-B and III seems like all is pretty balanced regardless of which engine you might lose. What am I missing?
16th Jul 2012, 16:17
Gulfstream (like all OEM's...I imagine) have to nominate/elect a "critical" engine for certification. As with GIV, V, 550 it is the right engine to allow for takeoffs with APU running and APU exhaust efflux adding an "extra" turning moment about the vertical axis I.e. if RH engine failed the APU exhaust would add to the yawning moment of nose to RHS. I don't claim to be an expert, but that is what I was told. I have flown GIV and 550 and I'm assuming that GII and III APU exhaust are also on RHS of the aircraft? Hope it answers your question.:ok:
16th Jul 2012, 18:59
I have never heard of the APU exhaust being the reason for a critical engine issue on any Gulfstream. This for sure does not hold true on the GII and GIII series aircraft because the APU is not certified for use in flight.
I have to be honest, I remember hearing the critical engine is the #2 engine but its been a long time since I flew or been in to school the 2's and 3's so I am still racking my brain to remember why. For sure they do not teach that there is a critical engine on the GIV-G550 in training these days. As far as systems, the aircraft are basically the same since the original G2 (except of course the electrical system and avionics). I will see if I can get a better answer for you and revert back.
davidjh.... interesting comment, about the APU.... This is taken from the GIV AFM 5.1-1. Either engine is considered to be the critical engine for engine failure.
Noise abatement procedure GIII
Utilize Min EPR and 20 Flaps for all takeoff rolls. Align aircraft on the runway as close to departure end as possible. Hold brakes and advance power levels to 80% RPM (N2). Release brakes and rapidly advance power levers to Min EPR. At VR promptly rotate the aircraft to a 13 degree nose up pitch attitude. Upon obtaining a positive rate of climb, retract landing gear, reduce flaps to 10 and accelerate through VFS, maintaining a 15 degree pitch attitude.
Taken from http://www.gulfstream.com/product_support/technical_pubs/pdfs/G2_G3/_OIS/G1159A_OIS-09%20Rev%2001.pdf
Remember that the AFM is based on single engine profiles, hence reason they state V2-V2+10 for best climb gradient. So look at the AFM V2 values, how close to 164 kts are they?
19th Jul 2012, 20:34
Mutt: been a while since I flew the GIV...thanks for setting me straight on the OM comment.
Nonya: G550 OM and AFM definitely say RH engine is critical...without giving reasons. About 3 months ago I did a G550 Sim instructors course with a Gulfstream (demo) pilot and asked him why RH engine? He told me same thing regarding APU. I guess I shouldn't share my info unless it's written somewhere hey?
12th Aug 2012, 12:07
Critical engine and flaps 10, first the critical engine.
When the G-2 was certified, the FAA required that a “critical engine” be identified. I think Gulfstream flipped a coin and since the right engine has the capability of providing combined hydraulic pressure via theutility system they picked that one. I just heard that through tribal knowledge. Also all G-2s and G-3 DCs do not have an airborne APU so whatever thrust the APU gives out is not there. All subsequent G-1159 series airplanes are based off of the G-2 certification (G-2, G-3 and G-IV).
Second the flaps 10 takeoff. I always used 20 flaps for all normal takeoff but once we had installed the Stage 3 hush kits they required aflaps 10 takeoff. We noticed better performance all the way around and reducedmain tire wear. The reason Stage 3 wanted flaps 10 takeoffs is because the airplane accelerated faster through the noise sensor. Thereby allowing less time in the “cone” and reducing measurable noise signature for certification.Stage 3 is more of a performance based noise reduction than an actual reductionin noise.
The tire wear issue puzzled me so we talked to an aerospace engineer.His explanation was that the pitching moment on rotation was less due to the increase speed therefore reducing the amount of down pressure exerted on the tires. This engineer stated that most tire wear was on rotation due to the weight and down pressure, not the landing. All I can say is that we increased tire wear by about 20% using flaps 10. Second segment climb is great too at flaps 10. I now use flaps 10 whenever able in G-2s, G-3s and G-IVs. I can’t speak for the rest of the fleet but I imagine it would be the same.
As far as climbing at V2+10, I don’t see the need to do so unless you have an engine failure, trying to avoid wake turbulence, terrain requirements or staying within the requirements of the hush kit requirements.